NORTHAMPTON NORTH WEST RELIEF ROAD · 2020-06-15 · 5.5 proposed cycle, walking and horse riding facilities 40 6 traffic impact assessment 44 6.1 introduction 44 6.2 modelling approach

NWRR-WSP-GEN-0000-RP-TR-00002 JUNE 2020 PUBLIC

Northamptonshire County Council

NORTHAMPTON NORTH WEST

RELIEF ROAD

Transport Assessment

Northamptonshire County Council

NORTHAMPTON NORTH WEST RELIEF ROAD

Transport Assessment

PUBLIC

TYPE OF DOCUMENT (VERSION) PUBLIC

PROJECT NO. 70021598

OUR REF. NO. NWRR-WSP-GEN-0000-RP-TR-00002

DATE: JUNE 2020

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NORTHAMPTON NORTH WEST RELIEF ROAD PUBLIC | WSP Project No.: 70021598 | Our Ref No.: NWRR-WSP-GEN-0000-RP-TR-00002 June 2020 Northamptonshire County Council

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Issue/revision First issue Revision 1 Revision 2 Revision 3

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Date 08/06/2020

Prepared by Karishma Khatri

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Authorised by Ian Braddock

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Project number 70021598

Report number NWRR-WSP-GEN-0000-RP-TR-00002

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CONTENTS

1 EXECUTIVE SUMMARY 1

2 INTRODUCTION 5

2.1 INTRODUCTION 5

2.2 BACKGROUND 5

2.3 PURPOSE OF THIS REPORT 6

2.4 SCOPE OF ASSESSMENT 6

2.5 STRUCTURE OF REPORT 7

3 POLICY REVIEW 8

3.1 INTRODUCTION 8

3.2 NATIONAL POLICY 8

3.3 REGIONAL POLICY 8

3.4 LOCAL POLICY 10

3.5 POLICY SUMMARY 12

4 EXISTING CONDITIONS 13

4.1 INTRODUCTION 13

4.2 SITE LOCATION 13

4.3 SURROUNDING AREA 14

4.4 WALKING, CYCLING AND EQUESTRIAN 14

4.5 SURROUNDING HIGHWAY NETWORK 16

4.6 EXISTING TRAFFIC CONDITIONS 19

4.7 PERSONAL INJURY COLLISIONS (PICS) 29

5 DEVELOPMENT PROPOSALS 36


5.1 INTRODUCTION 36

5.2 PROPOSED NORTH WEST RELIEF ROAD 36

5.3 PROPOSED NEW ACCESS JUNCTIONS 37

5.4 DALLINGTON GRANGE DEVELOPMENT 39

5.5 PROPOSED CYCLE, WALKING AND HORSE RIDING FACILITIES 40

6 TRAFFIC IMPACT ASSESSMENT 44

6.1 INTRODUCTION 44

6.2 MODELLING APPROACH 44

6.3 LOCAL HIGHWAY IMPACT ASSESSMENT 46

6.4 IMPACT ON PERSONAL INJURY COLLISIONS 63

6.5 WIDER BENEFITS OF NWRR SCHEME 64

6.6 SUMMARY 68

7 IMPACT ON INDIVIDUAL JUNCTIONS 70

7.1 INTRODUCTION 70

7.2 MODELLING APPROACH 71

7.3 JUNCTION CAPACITY ASSESSMENTS 72

7.4 SUMMARY 85

8 MITIGATION MEASURES 87

8.1 INTRODUCTION 87

8.2 MITIGATION SCHEMES (OVERVIEW) 87

8.3 MITIGATION SCHEME 1 88




8.7 SUMMARY 96

9 MONITOR & MANAGE STRATEGY 98


9.1 INTRODUCTION 98

9.2 PROPOSED MONITOR & MANAGE STRATEGY 98

9.3 J1: A508 HARBOROUGH ROAD / PITSFORD HIGH STREET PRIORITY JUNCTION 99

9.4 J2: A508 HARBOROUGH ROAD / BRAMPTON LANE PRIORITY JUNCTION 99

9.5 J8: ROMAN ROAD / NEW SANDY LANE / BERRYWOOD ROAD / SANDY LANE

PROPOSED ROUNDABOUT 100

9.6 SUMMARY 100

10 SUMMARY & CONCLUSIONS 102

TABLES

Table 4-1 – Details of PICs That Occurred at Key Locations Surrounding the Proposed

Scheme 30

Table 6-1 - 2031 Junctions Volume / Capacity Category (Minimal or Positive Impact) 55

Table 6-2 – 2031 Junction Volume / Capacity Category (Negative Impact) 55

Table 6-3 - 2031 With Scheme and Without Junctions Delay Category (Modelled Area) 61

Table 6-4 - 2031 With Scheme and Without Scheme Junction Delay Category for Key

Junctions Identified 62

Table 6-5 -Wider Traffic Benefits of the NWRR on Selected Links using NSTM flows 67

Table 7-1: A508 Harborough Road / Pitsford High Street Existing Priority Junction 73

Table 7-2 - A508 Harborough Road / Brampton Lane Existing Priority Junction 74

Table 7-3: A508 Harborough Road / Brampton Lane / Vyse Road Existing Roundabout 76

Table 7-4: A508 Harborough Road / A5076 Holly Lodge Existing Signalised Junction 77

Table 7-5: A5199 Northampton Road / Brampton Lane / Welford Road Existing Priority

Junction 79

Table 7-6 - A5199 Northampton Road / Brampton Lane / Welford Road Proposed

Roundabout 80

Table 7-7 - A5199 Northampton Road / Sandy Lane Existing Priority Junction 81

Table 7-8 - A5199 Northampton Road / Sandy Lane / NWRR Proposed Roundabout 82

Table 7-9 - A428 Harlestone Road / New Sandy Lane / York Road Existing Roundabout 83


Table 7-10 - Roman Road / New Sandy Lane / Berrywood Road / Sandy Lane Proposed

Roundabout 84

Table 8-1 - A508 Harborough Road / Brampton Lane / Vyse Road Mitigated Roundabout 92

Table 8-2 - A428 Harlestone Road / New Sandy Lane / York Road Mitigated Roundabout 94

Table 8-3 - A508 Harborough Road / A5076 Holly Lodge Mitigated Signalised Junction 95

Table 8-4 - Comparison of PRC Values in Existing & Mitigated Layout 96

FIGURES

Figure 3-1 - Committed Highway Schemes 11

Figure 4-1 - NWRR Scheme Location Overview 14

Figure 4-2 - Pedestrian, Cyclist and Equestrian Facilities 15

Figure 4-3 - Local Highway Network Surrounding The Proposed Scheme 17

Figure 4-4 - Signalised Crossing on Northampton Road facing Southwards 18

Figure 4-5 – 2015 Base Year AM Peak Actual Flow 21

Figure 4-6 - 2015 Base Year PM Peak Actual Flow 22

Figure 4-7 – 2015 Base Year AM Peak Junction V/C 24

Figure 4-8 - 2015 Base Year PM Peak Junction V/C 25

Figure 4-9 - 2015 Base Year AM Peak Junction Delay 27

Figure 4-10 – 2015 Base Year PM Peak Junction Delay 28

Figure 4-11 - PIC Plot A: Sandy Lane/Northamton Road/A5199 32

Figure 4-12 - PIC Plot B: Brampton Lane/Vyse Road/A508 33

Figure 4-13 - PIC Plot C: Brampton Lane/A508/High Street 34

Figure 4-14 - PIC Plot D: A508/A5076 35

Figure 5-1 - Full Orbital Route Schematic 37

Figure 5-2 - Proposed NWRR Access Junctions and downgraded section of A5199

Northampton Road (known as Causeway Link) 38

Figure 5-3 - NMU facilities proposed at the Sandy Lane / Northampton Road / NWRR

Roundabout 41


Figure 5-4 - NMU facilities proposed at the Northampton Road / Welford Road / Brampton

Lane Roundabout 42

Figure 6-1 – 2031 AM Peak Flow Difference Plot (With Scheme less Without Scheme) 47

Figure 6-2 - 2031 PM Peak Flow Difference Plot (With Scheme less Without Scheme) 48

Figure 6-3 – 2031 AM Without Scheme Junction Volume/ Capacity Ratio 51

Figure 6-4 - 2031 PM Without Scheme Junction Volume/ Capacity Ratio 52

Figure 6-5 - 2031 AM With Scheme Junction Volume/ Capacity Ratio 53

Figure 6-6 – 2031 PM With Scheme Junction Volume/ Capacity Ratio 54

Figure 6-7 - 2031 AM Without Scheme Junction Delay 57

Figure 6-8 - 2031 AM With Scheme Junction Delay 58

Figure 6-9 - 2031 PM Without Scheme Junction Delay 59

Figure 6-10 - 2031 PM With Scheme Junction Delay 60

Figure 7-1 - Assessed Junction Locations 71

Figure 8-1 – Locations of Traffic Calming Measures proposed in Boughton & Moulton 89

Figure 8-2 - A “Give way to oncoming vehicles” pinch point feature 90

Figure 8-3 - The “Give way to oncoming vehicles” pinch point feature located outside the

entrance of Boughton Primary School facing westbound 91

APPENDICES

LHA RESPONSE TO TAA

TRANSPORT ASSESSMENT SCOPING DOCUMENTS AND EMAILS

NORTHAMPTON CYCLE MAPS

PERSONAL INJURY COLLISION (PIC) DATA

NWRR GENERAL ARRANGEMENT DRAWINGS


DALLINGTON GRANGE ILLUSTRATIVE MASTERPLAN

NSTM PLOTS

JUNCTION MODELLING OUTPUT REPORTS (EXISTING & MITIGATED)

ROMAN ROAD / NEW SANDY LANE / BERRYWOOD ROAD / SANDY LANE PROPOSED

ROUNDABOUT

BOUGHTON & MOULTON NSTM PLOTS

MITIGATION SCHEME & MONITOR AND MANAGE DRAWINGS

NORTHAMPTON NORTH WEST RELIEF ROAD PUBLIC | WSP Project No.: 70021598 | Our Ref No.: NWRR-WSP-GEN-0000-RP-TR-00002 June 2020 Northamptonshire County Council Page 1 of 125

1 EXECUTIVE SUMMARY

1.1.1. A Transport Assessment (TA) has been prepared to support a planning application for a new relief

road being proposed to the north-west of Northampton called the North-West Relief Road (NWRR).

1.1.2. The NWRR will be the primary access route into the new Dallington Grange development which

received resolution to grant planning permission in November 2018 and is proposed to support the

additional traffic generated from this development. The NWRR will also help to ease the existing and

forecasted increasing traffic in Northampton Town as it will provide an alternative route option for

vehicles travelling through Northampton and surrounding villages.

1.1.3. A TA for the NWRR scheme was required because it is anticipated that some traffic will reroute and

alter their existing journey patterns to use the new road. Therefore, the TA has assessed the impact

that this rerouting traffic, as well as the newly generated traffic from the Dallington Grange, will likely

have on the surrounding existing road network and whether any measures are needed to mitigate

these impacts. In addition, the cycle, pedestrian and horse riding facilities associated with the

proposed scheme have been assessed to see if they are in line with current recommended policy and

guidance. The impact that re-routing traffic could have on Personal Injury Collisions (PICs) were also

assessed as part of the TA.

1.1.4. The TA only assesses the northern section of the NWRR being delivered by NCC (approximately

1.6km in length and includes the reconfiguration of two junctions along NWRR) and is referred to as

the “proposed scheme” in this TA. The southern section of the NWRR is to be delivered by the

developer of the Dallington Grange housing development site.

1.1.5. The TA demonstrates that the proposed scheme is supported by and adheres to both national and

local transport related policy and guidance. The proposed scheme caters for Non-Motorised Users

(NMUs), including pedestrians, cyclists and horse-riders, by incorporating a range of suitable NMU

facilities within the design.

1.1.6. Work was undertaken to model the NWRR in the Northamptonshire Strategic Transport Model (NSTM)

to understand how traffic will likely reroute and alter existing journey patterns to use the NWRR and

to understand what impact this traffic could have on the surrounding highway network.

1.1.7. Analysis of the NSTM indicated that the NWRR scheme is forecasted to provide significant travel

benefits to Northampton’s residents and users of the local highway network across the whole town

and also on outskirts of the town. More specifically, it will relieve traffic issues already present on the

network along the primary road corridors used for east to west trips in Northampton and relieve traffic

issues along the minor roads that have not been designed for heavy traffic volumes as well as those

utilised as alternative routes to avoid congestion. Whilst the benefits are far reaching, key areas

include:

A43 Lumbertubs Way;

A5076 Red House Road;

A428 Harlestone Road;

A4500 Weedon Road;

A508 Harborough Road;


Harlestone Road (The Bramptons); and

Mill Lane.

1.1.8. The proposed scheme will also provide additional infrastructure capacity to support movements

generated by forecast development and growth in the region. The key locations and corridors which

showed a reduction in traffic volumes as a result of the NWRR included:

Harlestone Road West of the New Sandy Lane Roundabout;

A508 Kingsthorpe Road / Harborough Road;

A45 Nene Valley Way and A5076 Mere Way;

Brampton Lane (between Lower Harlestone and Pitsford);

Harlestone Road (through the Bramptons); and

Eastern Avenue.

1.1.9. Furthermore, analysis demonstrated that the wider benefits of the NWRR include:

A reduction in traffic flows on a number of significant links and junctions in Northampton when

compared to the Do Minimum case (without the proposed scheme);

A very strong business case with a high Benefit/Cost Ratio (BCR) which demonstrates that the

savings, predominantly to travel time, outweigh the cost of delivering the scheme by 7 times, a very

high return for a transport scheme;

Additional capacity on the transport network to support housing growth targets; and

Additional resilience to the Northampton highway network when disruption arises from time to time,

such as planned roadworks, accidents or other foreseen and unforeseen events.

1.1.10. The junctions, at which the NSTM results indicate that the NWRR could have a negative impact were

assessed in more detail. Following the analysis of the individual junction modelling results it was

established that the following locations could experience significant traffic impacts as a result of the

proposed scheme:

The A508 Harborough Road / Pitsford High Street Priority Junction, particularly on the A508

Harborough Road South as there is no stacking capacity for vehicles to turn right;

The A508 Harborough Road / Brampton Lane Priority Junction, particularly on the A508

Harborough Road North as there is no stacking capacity for vehicles to turn right;

The A508 Harborough Road / Brampton Lane / Vyse Road Existing Roundabout, particularly on

the Vyse Road and Brampton Lane arms of the junction;

The A428 Harlestone Road / New Sandy Lane / York Road Roundabout; and

The Roman Road / New Sandy Lane / Berrywood Road / Sandy Lane Proposed Roundabout,

particularly on the Berrywood Road and New Sandy Lane arms of the junction.

1.1.11. In addition, analysis of the NSTM results highlighted that the proposed scheme would be likely to

increase the volume of vehicle traffic routing through the villages of Moulton and Boughton.

1.1.12. The TA identifies the following mitigation measures would be required to mitigate the forecast traffic

impact of the proposed scheme at the aforementioned locations:

Mitigation Scheme 1: Traffic Calming in Boughton and Moulton;

Mitigation Scheme 2: Capacity improvements at A508 Harborough Road / Brampton Lane / Vyse

Road Roundabout;


Mitigation Scheme 3: Capacity improvements at A428 Harlestone Road / New Sandy Lane / York

Road (NWRR) Roundabout; and

Mitigation Scheme 4: To help accommodate potential traffic flow diversions associated with

Mitigation Scheme 1, capacity improvements at the A508 Harborough Road / A5076 Holly Lodge

Drive Signalised Junction.

1.1.13. In addition to the mitigation measures proposed above, the remaining junctions which were identified

as being adversely impacted by the proposed scheme have been included in a Monitor and Manage

Strategy.

1.1.14. The Monitor and Manage Strategy is proposed to avoid short-term improvement schemes which may

have limited longevity due to various unknown variables which can make any such schemes abortive.

The locations of these junctions which are adversely impacted by the proposed scheme are influenced

by factors such as the phasing of committed development traffic, committed schemes or additional

infrastructure. These factors attribute to network changes which could influence how traffic is

distributed over time. Therefore, the performance of these junctions will be observed once the

proposed scheme is operational, with traffic counts being undertaken annually to understand the

impact of the reassignment of traffic prior to delivering any mitigation scheme.

1.1.15. The Monitor and Manage Strategy is proposed at the following junctions:

A508 Harborough Road / Pitsford High Street Priority Junction;

A508 Harborough Road / Brampton Lane Priority Junction; and

New Sandy Lane / Berrywood Road / Roman Road / Sandy Lane Proposed Roundabout.

1.1.16. Indicative layouts for potential mitigation schemes at the junctions have been produced to highlight

measures which could be implemented if mitigation were to be required following the monitor and

manage approach.

1.1.17. Overall, the TA finds that the proposed NWRR will provide benefits to the wider highway network.

These benefits include a reduction in the number of vehicles on certain roads in Northampton Town,

particularly residential areas which will result in less traffic and less congestion contributing to cleaner

air, safer roads and a healthier population in these areas. The proposed scheme is also expected to

provide additional infrastructure capacity to support movements generated by forecast development

and growth within the region.

1.1.18. Where the proposed scheme is forecast to have negative traffic impacts, the TA recommends that the

following should be considered when assessing the proposed scheme:

Any minor negative impacts caused as a result of the proposed scheme should be considered in

the context of the wider traffic benefits of the proposed scheme across the network as a whole;

The proposed scheme will create a balanced network of vehicles using existing and new

infrastructures proposed which will have a positive impact overall; and

Any minor negative impacts caused as a result of the proposed scheme can be mitigated where

appropriate through specific mitigation schemes or included in the Monitor and Manage Strategy.

1.1.19. Taking account of the above, this TA shows that the proposed scheme provides an overall net benefit

to Northampton’s highway network as any negative localised impacts caused as a result of the scheme


can be satisfactorily mitigated. As such, this TA concludes that the proposed scheme is acceptable in

terms of highways and transport impact.


2 INTRODUCTION

2.1 INTRODUCTION

2.1.1. WSP have been commissioned by Northamptonshire County Council (NCC) to prepare a Transport

Assessment (TA) to support a planning application for the northern section of a new relief road

proposed to the north-west of Northampton, referred to as the North-West Relief Road (NWRR).

2.1.2. The NWRR will be the primary access route into the new Sustainable Urban Extension known as

Dallington Grange development which received resolution to grant planning permission (ref no:

N/2014/1429) in November 2018 and is therefore proposed to support the additional traffic generated

from this development. The NWRR will also help to ease the existing and forecasted increasing

general traffic growth as it will provide an alternative route option for vehicles travelling through

Northampton Town and its surrounding villages.

2.1.3. The proposed NWRR is of single carriageway standard but designed to enable upgrading to dual

carriageway in the future if required. It will join to the existing road network at the A5199 Northampton

Road via a roundabout to the north and at the Harlestone Road / York Way / New Sandy Lane

Roundabout to the south.

2.1.4. The northern section of the NWRR (approximately 1.61km in length) is being delivered by NCC and

is the subject of this TA and throughout this report, this section will be referred to as the “proposed

scheme”. The remainder of the relief road is to be delivered by the developer of the Dallington Grange

site which will be located to the south-west of the proposed scheme. This is the southern section of

the NWRR which will join the existing highway network at the Harlestone Road / New Sandy Lane /

York Way roundabout.

2.1.5. It is anticipated that some traffic will reroute and alter their existing journey patterns to use the new

road once built. This TA assesses the impact that this rerouting traffic and the Dallington Grange traffic

will likely have on the surrounding existing road network and whether any measures are needed to

mitigate these impacts. In addition, the cycle, pedestrian and horse riding facilities associated with the

proposed scheme have been assessed to see if they are in line with and meet current recommended

policy and guidance. The impact that re-routing traffic could have on Personal Injury Collisions (PICs)

has also been assessed as part of this TA.

2.2 BACKGROUND

2.2.1. A planning application for the NWRR was submitted to NCC in June 2019 (Ref: 19/00045/CCDFUL)

and was supported by an original TA, produced by WSP in May 2019. The traffic modelling undertaken

in the original TA was based on the traffic flows derived from the Northamptonshire Strategic Transport

Model (NSTM), as agreed with Northamptonshire Highways (NH) Development Control Team.

2.2.2. Following the submission of the planning application in June 2019, WSP received a number of

comments from various parties in regard to the original TA. As a result, a Transport Assessment

Addendum (TAA) was submitted in September 2019 which addressed the responses below:

There were concerns regarding how representative the future traffic flows extracted from the NSTM

were likely to be of the traffic conditions experienced in reality;


Concerns were raised over the forecast level of future operational performance and the associated

forecast vehicle queuing and delay for the proposed NWRR junctions; and

The mitigation measures proposed within the original TA would need to be developed further and

assessed which would involve undertaking further capacity assessments and providing

accompanying design drawings where appropriate.

2.2.3. Following the submission of the TAA and associated documentation which accompanied the

application, the Local Highway Authority (LHA ) accepted the proposals subject to planning conditions.

Their response dated 8th November 2019 is provided in Appendix A of this report.

2.3 PURPOSE OF THIS REPORT

2.3.1. Since the submission of the above, the NSTM has been updated following receipt of latest traffic flows

and updated committed development information.

2.3.2. The purpose of this report is to provide an updated TA to account for the changes in the NSTM and

subsequent traffic modelling undertaken. This report therefore supersedes the previous submitted TA

(May 2019) and subsequent TAA (September 2019).

2.3.3. The localised NSTM model utilised in this TA, has been recalibrated and validated in accordance with

the Transport Analysis Guidance (TAG)1 with the latest traffic flows and thus a robust assessment has

been undertaken in the production of the TA.

2.4 SCOPE OF ASSESSMENT

2.4.1. A scoping note and associated email responses from NH are contained within Appendix B.

2.4.2. The scope of this assessment has been agreed with NH’s Development Control Team as follows:

Consideration of relevant planning and transport-related planning policy;

Consideration of baseline transport conditions, including:

- Traffic conditions on the surrounding local road network;

- Pedestrian facilities;

- Cycle facilities;

- Equestrian facilities; and

- PICs that occurred on the surrounding local road network.

Description of the NWRR proposal, including:

- Clarification of the extent of the NWRR that is subject to this assessment;

- Proposed new access junctions;

- The Dallington Grange Development; and

1 TAG is the online transport analysis guidance provided by the Department for Transport (DfT) that provides information on the role of transport modelling and appraisal. TAG provides guidance by which a strategic transport model should be validated to prove that it is fit for purpose to assess a proposed scheme.


- The walking, cycling and horse-riding facilities that are proposed as part of the scheme.

Undertaking a traffic impact assessment to understand the impacts that re-routing vehicle trips

are likely to have on the local highway network:

- The modelling approach used to inform the traffic impact assessments;

- The assumptions of the NSTM and modelled scenarios;

- The Area of Influence (AOI) and individual junction capacity assessments; and

- The performance of the local highway network without and with the proposed NWRR

scheme.

Consideration of any mitigation measures on the local highway network in light of the traffic

impact assessment; and

Consideration of the wider benefits of the NWRR scheme.

2.5 STRUCTURE OF REPORT

2.5.1. The report is structured as follows:

Chapter 3 summarises the relevant national, local policies and objectives;

Chapter 4 sets out the baseline transport conditions in the local area;

Chapter 5 presents an overview of the NWRR proposals and clarifies the extent of the NWRR that

is subject to this assessment;

Chapter 6 details the operational performance of the local highway network without and with the

proposed NWRR scheme and assesses the impact that building the NWRR would likely have on

the surrounding road network. This chapter also presents the wider benefits of the proposed

scheme, including the key findings from the proposed scheme business case and traffic flow

benefits of the wider area;

Chapter 7 assesses the impacts of the proposed NWRR scheme on individual junctions on the

surrounding highway network;

Chapter 8 sets out the mitigation proposals deemed necessary;

Chapter 9 sets out the Monitor and Manage Strategy proposed as part of the scheme; and

Chapter 10 provides a summary and concludes this TA.


3 POLICY REVIEW

3.1 INTRODUCTION

3.1.1. This section of the report considers the local, regional and national transport related planning policy

context of the proposals.

3.2 NATIONAL POLICY

National Planning Policy Framework, February 2019

3.2.1. The Ministry of Housing, Communities and Local Government published the revised National Planning

Policy Framework (NPPF) in July 2018. Following technical consultation on updates to the national

planning policy, an updated version has been published in February 2019.

3.2.2. Paragraph 111 of the NPPF states that, “All developments that will generate significant amounts of

movement should be required to provide a travel plan, and the application should be supported by a

transport statement or transport assessment”.

3.2.3. It is anticipated that the NWRR will cause traffic to reroute and alter their existing journey patterns to

use the new road and thus will generate a significant amount of new and changed movement on the

surrounding road network. A TA is thus required to determine the impact the NWRR is likely to have

on highway safety and the surrounding highway network.

3.2.4. Paragraph 109 of the NPFF states that, “Development should only be prevented or refused on

highways grounds if there would be an unacceptable impact on highway safety, or the residual

cumulative impacts on the road network would be severe”.

3.2.5. This TA demonstrates that the proposed scheme will not impact the safety of the surrounding road

network, nor will it exacerbate any existing safety concerns. This TA also demonstrates that any

negative impacts caused as a result of the proposed scheme can be mitigated where appropriate to

ensure that the cumulative impact on the local highway network is not severe.

3.3 REGIONAL POLICY

The West Northamptonshire Joint Core Strategy, December 2014

3.3.1. The Joint Core Strategy (JCS) sets out the long-term vision and objectives for the whole of the West

Northamptonshire area for the plan period up to 2029, including strategic policies for steering and

shaping development.

3.3.2. The infrastructure section of the document considers that “new development will be supported by and

provide good access to infrastructure” and that “where development generates a need for new

infrastructure, developers will need to demonstrate that provision will be made to meet the necessary

requirements”.

3.3.3. The document also states that “New development will only be permitted if the necessary on and off-

site infrastructure that is required to support it, and mitigate its impact, is either already in place, or

there is a reliable mechanism in place to ensure that it will be delivered”.


3.3.4. Policy N1 of the JCS states the ‘Regeneration of Northampton’ will be supported by the following

measures:

“Housing development within the existing urban area through urban capacity infill and Sustainable

Urban Extensions at Northampton North, Northampton West, Northampton South, Northampton

South of Brackmills, Northampton Kings Heath, Northampton North of Whitehills, Northampton

Norwood Farm/ Upton Lodge and Northampton Upton Park;

Redevelopment at existing employment sites and SEMLEP Northampton Waterside Enterprise

Zone, with major office and service development focused on the central area;

Provision of local shopping, services and supporting facilities within identified Sustainable Urban

Extensions; and

Improvements to the transport network, public transport, cycling and walking facilities within

Northampton to improve connectivity, safety and journey reliability”.

3.3.5. Considering the above, it is clear that the NWRR is needed to support the Dallington Grange

development, as well as other future committed development. The TA also demonstrates that that any

negative impacts caused as a result of the proposed scheme can be mitigated where appropriate.

JCS Supporting Document: Infrastructure Delivery Plan, September 2017

3.3.6. The Infrastructure Delivery Plan (IDP) aims to identify the strategic priorities for the delivery of key

infrastructure needed to support the implementation of the JCS over the plan period 2011-2031 as

required in the National Planning Policy Framework (NPPF).

3.3.7. In Section 3.24 under Delivered and Funded Infrastructure, it is reiterated that, “It is important for

housing growth to be matched by the necessary and place shaping infrastructure in order to create a

place that meets the vision and aims of the area”.

3.3.8. Again, it is clear that the NWRR is therefore needed to support the visions and aims of the local area,

especially in relation to housing growth and economic prosperity.

The Central Area Action plan (CAAP), January 2013

3.3.9. The CAAP provides a series of consistent and clear policies aimed at securing the improvement and

extension of Northampton’s Central Area whilst seeking to protect the town’s historic built character

and open spaces. The plan, “takes into account other current plans and strategies including the East

Midlands Regional Spatial Strategy and the West Northamptonshire Joint Core Strategy”, which

provide the, “overarching strategic principles for the CAAP”.

3.3.10. The CAAP sets out a sustainability appraisal methodology aimed at appraising the economic effects

of strategies and policies in a local development document. Under the Material Assets Topic: SA14,

one of the objectives is to, “ensure that the housing stock and associated infrastructure meets the

needs of the local people”.

3.3.11. The Cumulative Effects section of the CAAP outlines potential cumulative effects as a result of

infrastructure projects serving developments in north-west Northampton, including the Sandy Lane

Relief Road and Northampton North West By-Pass (also known as the NWRR). It specifies that,

“application of these policies should result in a reduction in unnecessary car use, so the network

improvements will support economic growth”, and that, “the West Northamptonshire Joint Core

Strategy and CAAP are likely to ensure that the cumulative effect will be a minor positive”.


3.4 LOCAL POLICY

Northampton Local Development Scheme (LDS), February 2017

3.4.1. The Northampton LDS is a continuing plan for the preparation of key planning policy documents. The

LDS covers the key following documents and they relate to each other:

Northampton Local Plans (saved polices) - Adopted 1997;

Northampton Central Area Action Plan – Adopted 2013;

West Northamptonshire Joint Core Strategy Local Plan Part 1 – Adopted 2014; and

Northamptonshire Minerals and Waste Local Plan – Adopted 2014.

Northamptonshire Transportation Plan, 2012

3.4.2. The Northamptonshire Transportation Plan was adopted in April 2012 and sets out

Northamptonshire’s proposed transport goals and priorities from April 2012 onwards.

3.4.3. The plan states NCC’s aim (Strategic Policy 3) is to ensure that all new developments are well

connected to walking and cycling routes which connect to the existing transport network and NCC’s

aim to generally improve the walking and cycling infrastructure across the County to make cycling and

walking viable options for how people travel in Northamptonshire.

Northampton Town Transport Strategy, 2013

3.4.4. The Northampton Town Transport Strategy2 is one of a series of thematic daughter documents to the

Northamptonshire Transportation Plan (set out above). The Northampton Town Transport Strategy

sets out the overarching vision for transport in Northampton and details the strategy to achieve it.

3.4.5. Chapter 5 of the document (titled Highway Strategy) states that “three new road links will provide the

additional highway capacity necessary to support the growth proposals and improve strategic

connections. These sections of new highway infrastructure will be supported by a variety of junction

improvement and smaller schemes”.

3.4.6. The following three road schemes are identified in the Northampton Town Transport Strategy and

illustrated in Figure 3-1:

Completion of the Sandy Lane Relief Road;

Construction of the North – West Bypass, linking the A428 Harlestone Road and the A5199 Welford

Road; and

A43 dualling north of Northampton.

2 Northamptonshire County Council: Northampton Town Strategy (January 2013). Accessed online via https://www.northamptonshire.gov.uk/councilservices/northamptonshire-highways/transport-plans-and-policies/Documents/Northampton%20Town%20Transport%20Strategy.pdf

https://www.northamptonshire.gov.uk/councilservices/northamptonshire-highways/transport-plans-and-policies/Documents/Northampton%20Town%20Transport%20Strategy.pdf

https://www.northamptonshire.gov.uk/councilservices/northamptonshire-highways/transport-plans-and-policies/Documents/Northampton%20Town%20Transport%20Strategy.pdf


Figure 3-1 - Committed Highway Schemes

Source: Northampton Town Strategy (January 2013)

3.4.7. The North West Bypass as referred in Northampton Town Strategy effectively makes up the northern

section of the NWRR (which is the subject of this TA) and the southern section of the NWRR which is

to be delivered by the developer of the Dallington Grange development.

3.4.8. The NWRR is therefore supported by local policy as the proposed scheme is needed to provide

additional highway capacity to support Northampton’s growth proposals.

Northamptonshire Arc

3.4.9. Northamptonshire Arc has been adopted by the council to help guide its investment activities and has

secured wider support from other local partners. It is also used to help secure private sector and

central government investment and attract businesses and jobs into the area.

3.4.10. The Northamptonshire Arc document is a locally developed spatial concept covering the whole county

representing an integrated approach to economic development, the environment and connectivity. It

is underpinned by the pursuit of three high level outcomes which are:

Transformed connectivity;

A naturally resilient and low carbon Northamptonshire; and

A stronger and greener economy.


3.4.11. The Connecting Northamptonshire3 (October 2011) document makes up part of the Northamptonshire

Arc Publications, but focuses primarily on connectivity, including transport, broadband provision and

access.

3.4.12. Page 8 of the document states that “Northamptonshire is committed to addressing ’infrastructure gaps’

in the road network, making car travel more sustainable and managing traffic better”. The document

explains that parts of the strategic network experience congestion which is already having a negative

impact on economic performance and quality of life. There are concerns that as road traffic grows,

congestion will become more of an issue which could be exacerbated by the large scale housing

developments planned for the county.

3.4.13. Figure 5 of the document illustrates the strategic road connections which provide the main arteries for

economic growth within Northamptonshire. The text underneath the figure states that ‘Northampton’s

Radial Routes’ are in need of an upgrade; this includes the connections through the Dallington Grange

development.

3.4.14. The NWRR makes up part of ‘Northampton’s Radial Routes’ and is therefore needed to support

economic growth, as well as future housing developments which are planned throughout the country.

3.5 POLICY SUMMARY

3.5.1. It is considered that the proposed scheme supported by this Transport Assessment takes into

consideration and adheres to the relevant national and local transport related policy and guidance

summarised above. This is demonstrated in the following sections of this Transport Assessment.

3 Northamptonshire County Council: Northamptonshire Arc Connecting Northamptonshire (October 2011). Assessed online via: https://www.northamptonshire.gov.uk/councilservices/business-and-economy/our-projects/Documents/ConnectingNorthamptonshire_FinalMar2012_lowres.pdf

https://www.northamptonshire.gov.uk/councilservices/business-and-economy/our-projects/Documents/ConnectingNorthamptonshire_FinalMar2012_lowres.pdf

https://www.northamptonshire.gov.uk/councilservices/business-and-economy/our-projects/Documents/ConnectingNorthamptonshire_FinalMar2012_lowres.pdf


4 EXISTING CONDITIONS

4.1 INTRODUCTION

4.1.1. This section of the report sets out the baseline transport conditions at and near the proposed scheme,

including existing traffic conditions and base year results from The Northamptonshire Strategic

Transport Model (NSTM). This section of the report considers the following elements:

The site location;

The surrounding area;

Existing sustainable travel including walking, cycling and horse riding;

Surrounding highway network;

Existing traffic conditions;

Base year NSTM results; and

Personal injury collisions (PICS).

4.1.2. The existing public transport services have been assessed and remain unchanged. The proposed

scheme has no impact on these facilities and therefore public transport services have not been

addressed in this report.

4.2 SITE LOCATION

4.2.1. The North-West Relief Road (NWRR) is a new relief road proposed to the north-west of Northampton.

The northern section of the NWRR is approximately 1.6km in length and is being delivered by NCC

and is the subject of this TA. The southern section of the NWRR is being delivered by the developer

of the Dallington Grange site which will be located to the south-west of the proposed scheme (see

paragraph 5.4 for more details about Dallington Grange).

4.2.2. Figure 4-1 (overleaf) illustrates the extents of both the northern and southern section sections of the

NWRR in the context of the Dallington Grange site location. This Figure also provides the details of

the Sandy Lane Relief Road providing context of the planned schemes in the vicinity of the proposed

scheme.


Figure 4-1 - NWRR Scheme Location Overview

4.3 SURROUNDING AREA

4.3.1. The proposed scheme is situated to the north west of Northampton; west of the A508 and Boughton,

and east of the Harlestone Nature Reserve and the Brampton Heath Golf Centre. The proposed

scheme crosses the Rugby to Milton Keynes railway line to the south.

4.3.2. The ‘site’ is defined as the area of land considered suitable for development of the proposed scheme.

The site boundary is roughly defined by the A5199 Welford Road and Sandy Lane to the north, the

Brampton Heath Golf Centre to the west, the River Nene to the east, and the Rugby to Milton Keynes

railway line to the south. The site boundary in shown in the General Arrangement drawing contained

within Appendix E.

4.3.3. The site consists largely of agricultural fields which are intersected by small areas of woodland,

hedgerows, and drainage channels that feed into the River Nene.

4.4 WALKING, CYCLING AND EQUESTRIAN

4.4.1. This section of the report sets out the walking, cycling and equestrian facilities that currently exist in

the area surrounding the proposed scheme.


4.4.2. The area around the proposed scheme currently benefits from a good standard of pedestrian, cyclist

and horse riding provision, with footpaths, bridleways and cycle routes offering connections to various

destinations and facilities. Figure 4-2 below shows the pedestrian, cyclist and equestrian facilities in

the vicinity of the proposed scheme.

Figure 4-2 - Pedestrian, Cyclist and Equestrian Facilities

WALKING

4.4.3. The Northamptonshire Public Rights of Way Definitive Map shows that there is an extensive network

of public footpaths located to the north-west of Northampton linking the villages of Harlestone, Church

Brampton, Chapel Brampton and Holdenby to one another and the outer edges of Northampton. In

addition, there are designated public footpaths located to the north of Northampton routing to and

through the villages of Boughton, Moulton and Pitsford.

4.4.4. There are no national trails but there are four long distance walking routes within 5km of the study

area including:

The Northamptonshire Round;

Brampton Valley Way;

Midshires Way; and

Macmillan Way - Boston to Abbotsbury.


4.4.5. In addition, it should be noted that many of the local highways that currently exist in the area

surrounding the proposed scheme include pedestrian footways, particularly in the built up and

residential areas.

CYCLING

4.4.6. National Cycle Route (NCR) 6 is a dedicated off-road cycle route which is located approximately 250m

to the east of the proposed scheme, routing north-south almost parallel with the scheme’s proposed

route. The route is part of the National Cycle Network (NCN) which is the national cycling route network

in the United Kingdom and was established to encourage cycling throughout Britain, as well as for the

purposes of cycle touring. The section of the route near the proposed scheme is well signposted,

indicating a shared used for pedestrians and cyclists.

4.4.7. In addition to NCR 6, a designated shared-use footway/cycleway exists on the eastern side of Welford

Road, routing all the way to Harborough Road through Kingsthorpe Village. A designated shared-use

footway/cycleway also exists on the southern side of Brampton Lane, routing all the way to the A508

/ Vyse Road / Brampton Lane Roundabout past the newly built Buckton Fields housing development.

These shared-use footways/cycleways provide cyclists with access and egress from the NCR 6

(Brampton Valley Way) close to the Brampton Lane / Welford Road / Northampton Road Junction.

Appendix C contains the Northampton Cycle Map which shows the cycle facilities across the whole

of Northampton.

4.4.8. Norbital (route 539) is an 29km (18 mile) circular cycle route around Northampton, which connects

residential areas with areas of employment and education such as the University of Northampton,

Brackmills and Moulton Park. The north-western section of the route provides access to Brampton

Valley Way via a signed off-road cycle path which crosses the railway line via Mill Lane (approximately

1.5km south of the proposed scheme). Appendix C contains a map of Norbital and other Key

Northampton Cycle Routes.

HORSE RIDING

4.4.9. There are several bridleways, which horse riders, pedestrians and cyclists can use within the vicinity

of the proposed scheme, as shown in Figure 4-2 above. A description of the bridleways located

closest to the proposed scheme is provided below.

4.4.10. HW6 is a bridleway running in a north-west to south-east alignment along the southern boundary of

the proposed scheme (the northern boundary of the proposed Dallington Grange scheme). From east

to west, Bridleway HW6 routes from Mill Lane in Kings Heath (south of the proposed scheme) in a

north-westerly direction until it meets public footpath HW44. From here the bridleway routes roughly

eastwards until it joins bridleway CC6 and the wider footpath and bridleway network located to the

north of Northampton (west of the proposed scheme).

4.5 SURROUNDING HIGHWAY NETWORK

4.5.1. The local highway network in the vicinity of the proposed scheme is illustrated in Figure 4-3 and the

most relevant links are described below.


Figure 4-3 - Local Highway Network Surrounding The Proposed Scheme

4.5.2. As stated in paragraph 2.1.4, the northern section of the NWRR (approximately 1.61km in length) is

being delivered by NCC (and is the subject of this TA) whilst the southern section is being delivered

by the developer of the Dallington Grange housing development site. The northern section (the

proposed scheme) will join the existing highway network at a new roundabout junction with Sandy

Lane and the A5199 Northampton Road. The southern section of the NWRR will join the existing

highway network at the Harlestone Road / New Sandy Lane / York Way Roundabout.

4.5.3. Sandy Lane is a single carriageway road which is subject to a 40 mile per hour (mph) speed limit and

is approximately 1.5km in length. Extending north-westwards from the A5199 Northampton Road,

Sandy Lane routes through Church Brampton Village until it reaches the junction with Harlestone

Road, thereafter Sandy Lane becomes Holdenby Road after its junction with Church Lane.

4.5.4. The A5199 Northampton Road is a single carriageway road which connects the village of Chapel

Brampton to the north-western outskirts of Northampton. The section of the A5199 Northampton Road

which routes closest to the proposed scheme is subject to a 40mph speed limit, whilst the northern

section of the road, from just north of the existing A5199 Northampton Road / Sandy Lane priority

junction to Chapel Brampton, is subject to the national speed limit. A controlled signalised toucan

crossing is provided at the junction between Northampton Road and NCR 6 enabling Non-Motorised


Users (NMUs) to cross Northampton Road to access and egress Brampton Valley Way and NCR 6

(see Figure 4-4 below).

Figure 4-4 - Signalised Crossing on Northampton Road facing Southwards

4.5.5. South of the existing A5199 Northampton Road / Brampton Lane / Welford Road priority junction, the

A5199 Northampton Road joins the A5199 Welford Road which routes southwards into the

Kingsthorpe Village area of Northampton. The A5199 Welford Road is of a wide single carriageway

standard and is subject to a 40mph speed limit on the northern section of the road until the pedestrian

crossing, located just north of the A5199 Welford Road / North Western Avenue priority junction.

Thereafter, the speed limit on the A51999 Welford Road reduces to 30mph. To the south, the A5199

Welford Road routes to Kingsthorpe Village Centre joining the A508 Harborough Road at a signalised

junction. The A5199 Welford Road primarily routes through a residential area fronted with set-back

residential properties on either side whilst also routing past two recreational grounds: Spring

Recreation Ground and Kingsthorpe Recreation Ground.

4.5.6. Brampton Lane is located to the east of the proposed scheme and is a single carriageway road that

is subject to a 40mph speed limit. At its most eastern end, Brampton Lane meets the A508 Harborough

Road at the A508 Harborough Road / Vyse Road / Brampton Lane Roundabout. The Brampton Lane

/ Home Farm Drive Roundabout, located on the eastern section of Brampton Lane, is the primary

vehicle access to the currently built section of the Buckton Fields mixed use development. The

development will have its own primary school, convenient local shops and services, open parkland

and play spaces when fully developed.

4.5.7. The A508 Harborough Road acts as a primary access for vehicles routing in and out of Northampton

from areas to the north of Northampton. The road is of single carriageway standard with mainly one


lane of traffic in each direction, apart from on the approaches to some junctions where additional traffic

lanes are added to the carriageway to facilitate movements at junctions. To the north of the A508

Harborough Road / Vyse Road / Brampton Lane Roundabout, the A508 Harborough Road routes to

and through the villages of Pitsford, Brixworth, Hanging Houghton, Lamport and eventually to Market

Harborough.

4.6 EXISTING TRAFFIC CONDITIONS

4.6.1. The Northamptonshire Strategic Transport Model (NSTM) has been utilised to inform the existing

(baseline) traffic conditions presented in this section of the report. The NSTM is a Simulation and

Assignment of Traffic to Urban Road Networks (SATURN) model which is a suite of flexible network

analysis computer programs that calculates transport assignment on road networks. The existing

traffic conditions provide a representation of traffic along the local highway network, without the NWRR

and Dallington Grange developments in place.

4.6.2. The model was originally calibrated and validated for the baseline year of 2015, using extensive traffic

survey data collated that same year. Following submission of the original TA (May 2019) and

subsequent TAA (September 2019), concerns were raised regarding how representative the traffic

flows extracted from the NSTM were likely to be of the traffic conditions experienced in reality. As a

result, the base NSTM local model has been recalibrated and validated with traffic count data collected

from surveys undertaken in May 2019 for an average weekday at several locations in the proximity of

the proposed scheme (refer to paragraph 6.2.8 for further details).

4.6.3. The 2019 count data has been brought back to a 2015 level using TEMPro growth rates as the NSTM

was originally developed for a 2015 base year. TEMPro is a program developed by the Department

for Transport (DfT), providing traffic growth projections used in transport models and intended to act

as a nationwide standardised distribution of growth in trip ends. The updated NSTM used in this

assessment therefore provides a more realistic and robust assessment of the baseline traffic

conditions along the local highway network.

BASE YEAR NSTM RESULTS

4.6.4. The following section details the results from the 2015 baseline NSTM modelling scenario

summarising the following:

The modelled traffic flows on the roads surrounding the proposed scheme;

The modelled Volume Capacity Ratio (V/C) at the junctions surrounding the proposed scheme; and

The modelled delay at the junctions surrounding the proposed scheme.

Modelled Traffic Flows

4.6.5. Figure 4-5 and Figure 4-6 (overleaf) illustrate the modelled traffic flows on the roads surrounding the

proposed scheme for the 2015 base year AM (08:00 – 09:00) and PM (17:00 – 18:00) peak hours

respectively. The plots display the actual traffic flow in Passenger Car Units (PCUs) per hour and level

of flow is indicated using bandwidths (thickness of the green lines on the roads), as classified in the

legend.

4.6.6. As expected, both plots show high volumes of traffic using the primary roads, particularly roads routing

into and around Northampton Town Centre. Roads near the proposed scheme that are modelled to

have high traffic flows in 2015 include:


A43 Lumbertubs Way;



A4500 Weedon Road; Harlestone Road (The Bramptons); and

Mill Lane;

4.6.7. It should be noted that Harlestone Road (through Church Brampton and Chapel Brampton), Bants

Lane and Mill Lane are shown to have high traffic flows. Given that that these links are local minor

roads and not designed for heavy traffic volumes, it is reasonable to suggest that drivers are using

these roads to make orbital movements around Northampton.


Figure 4-5 – 2015 Base Year AM Peak Actual Flow


Figure 4-6 - 2015 Base Year PM Peak Actual Flow


Modelled Volume Capacity Ratio (V/C)

4.6.8. Figure 4-7 and Figure 4-8 below show the modelled Volume Capacity Ratio (V/C) at junctions

surrounding the proposed scheme for the 2015 base year AM and PM peak hours respectively.

4.6.9. V/C is used as an indicator of congestion at a junction. Junctions which experience volumes of traffic

approaching their capacity level, typically a V/C of greater than 85%, will begin to experience

increased delay and are likely to be affected by operational constraints, i.e. begin to not be able to

facilitate the movement of all the traffic that wants to use it leading to queueing and increasing delay.

4.6.10. In the AM peak Figure 4-7 shows that none of the junctions within vicinity of the proposed scheme

show V/C greater than 85%. A similar pattern is presented in the PM peak, with only the Lumbertubs

Way / St Gregory’s Road junction in the wider area showing V/C greater than 85%.

4.6.11. It should be noted that Figure 4-7 and Figure 4-8 show that some junctions on Mill Lane have a V/C

between 75% and 85% suggesting that these junctions are approaching the 85% capacity level where

they will begin to experience increased delay and are likely to be affected by operational constraints.

These junctions are the Mill Lane / Tollgate Close and Harlestone Road / Mill Lane in the AM peak

and Mill Lane / Tollgate Close and Witham Way / Mill Lane in the PM peak.


Figure 4-7 – 2015 Base Year AM Peak Junction V/C


Figure 4-8 - 2015 Base Year PM Peak Junction V/C


Modelled Junction Delay

4.6.12. Figure 4-9 and Figure 4-10 present the modelled delay at the junctions surrounding the proposed

scheme for the 2015 base year AM and PM peak hours respectively. The delay is reported in seconds

and is the average delay experienced by each PCU across the modelled time period.

4.6.13. The level of delay is indicated by the size of the points identifying the junction, as classified in the

legend. The highest levels of delay are seen within Northampton Town Centre and further east and

south west of the proposed NWRR. Within the vicinity of the proposed NWRR delay does not exceed

90 seconds per PCU in both time periods.


Figure 4-9 - 2015 Base Year AM Peak Junction Delay


Figure 4-10 – 2015 Base Year PM Peak Junction Delay


Summary

4.6.14. The results from the 2015 baseline NSTM modelling AM and PM peak scenarios, summarised above,

indicate the following regarding the existing traffic conditions on the roads surrounding the proposed

scheme:

Primary roads, particularly roads routing into and around Northampton Town Centre, experience

the most traffic flows routing on them. Of note, there are currently large flows on the A428

Harlestone Road and the A4500 Weedon Road corridors, both of which the NWRR will relieve.

Within the study area, consisting of the Town Centre and the northern approaches to the Town,

junctions where north-south corridors meet those travelling east-west show that they’re in the 50-

75% capacity band, leaving some room for future development but less than may be desired. These

corridors and intersections will benefit from the NWRR scheme.

The modelling shows Harlestone Road (through Church Brampton and Chapel Brampton), Bants

Lane and Mill Lane to experience high traffic flows, suggesting that drivers are using these local

minor roads to make orbital movements around Northampton; and

Junctions on Mill Lane are approaching a capacity level where they will begin to experience

increased delay and are likely to be affected by operational constraints. By providing an alternative

east-west link, the NWRR will relieve capacity issues at Harlestone Road and Mill Lane which will

benefit those living in the towns and villages along the corridor.

4.6.15. The above findings have been used to identify the effect that the NWRR will likely have on existing

traffic conditions in and around Northampton. These findings are similar to the previous NSTM results

presented in the original TA dated May 2019.

4.7 PERSONAL INJURY COLLISIONS (PICS)

4.7.1. Personal Injury Collision (PIC) data has been obtained from Northamptonshire Highways (NH),

covering the period 26/07/2014 to 17/06/2018 at key locations surrounding the proposed scheme.

4.7.2. Table 4-1 shows the available details of the PICs that occurred at these locations between 26/07/2014

to 17/06/2018 with full details provided in Appendix D.

4.7.3. In order to ascertain whether there have been any further incidents recorded in the vicinity of the site

since the submission of the original TA (May 2019), CRASHMAP4 has been investigated for the

remaining period of 2018 and 2019. The data revealed that there have been no further incidents at

the key locations surrounding the proposed scheme during that time. Therefore, the analysis

presented below is still representative for the study area.

4 https://www.crashmap.co.uk/Search

https://www.crashmap.co.uk/Search


Table 4-1 – Details of PICs That Occurred at Key Locations Surrounding the Proposed Scheme

Accident Reference

WD121816 WN199215 WD064217 D029318 WD045316 WD181114 WD284915 WD053217 D041518 WN120316 WN136416 N089918

Severity Slight Slight Slight Slight Serious Slight Serious Slight Slight Slight Slight Slight

Number of Vehicles Involved

2 2 2 2 1 3 1 2 2 4 2 2

Number of Casualties

1 1 1 1 1 1 1 1 1 1 1 1

Date 19/05/2016 02/08/2015 07/09/2017 13/04/2018 24/02/2016 26/07/2014 04/10/2015 30/06/2017 17/06/2018 19/09/2016 15/11/2016 13/11/2018

Day Thursday Sunday Thursday Friday Wednesday Saturday Sunday Friday Sunday Monday Tuesday Wednesday

Time 13:15:00 15:10:00 05:30:00 14:10:00 05:40:00 09:33:00 01:15:00 08:40:00 14:15:00 15:55:00 14:30:00 14:40:00

Weather Fine (without

high wind) Fine (without











high wind)

Lighting Daylight Daylight Darkness

(street lights present and lit)

Daylight Darkness

(street lights present and lit)

Daylight Darkness (street

lights present and lit)

Daylight Daylight Daylight Daylight Daylight

Manoeuvre

Going ahead other / Going

ahead but held up

Turning right / Waiting to turn

right


ahead but held up

Turning right / Turning right

Going ahead other

Turning right / Going ahead

other

Going ahead other

Going ahead other / Waiting

to turn right

Overtaking stat vehicle O/S /

Waiting to turn right


ahead but held up / Turning right

Going ahead other / Turning

right

Going ahead other /

Turning right


Accident Reference

WD121816 WN199215 WD064217 D029318 WD045316 WD181114 WD284915 WD053217 D041518 WN120316 WN136416 N089918

Severity Slight Slight Slight Slight Serious Slight Serious Slight Slight Slight Slight Slight

Speed Limit 40 30 40 40 40 60 60 60 50 30 30 30

Road Conditions

Dry Dry Dry Dry Frost/Ice Dry Dry Dry Dry Wet/Damp Wet/Damp Wet/Damp

Vehicle 1 Type Car Car Car Car Van Car Car Car Bus Car Car Car

Vehicle 2 Type Car Van Car Car Car Car Cycle Car Car Car

Vehicle 3 Type Car Car

Vehicle 4 Type Car


4.7.4. Table 4-1 shows that a total of 12 PICs were recorded in the analysis area of which only 2 were

classified as serious and 10 were classified as slight.

4.7.5. Figure 4-11 to Figure 4-14 below show where the PICs detailed in Table 4-1 occurred.

Figure 4-11 - PIC Plot A: Sandy Lane/Northamton Road/A5199

4.7.6. Figure 4-11 shows the existing road network at the area where the new access junctions at the

northern end of the NWRR are being proposed.

4.7.7. Figure 4-11 shows that four PICs, ranging from a classification of serious to slight, occurred at or near

the A5199 Northampton Road / Sandy Lane priority junction and the A5199 Northampton Road /

Brampton Lane / Welford Road priority junction with three of these PICs occurring at the A5199

Northampton Road / Brampton Lane priority junction.

4.7.8. Further analysis of these PICs revealed that all three of the PICs that occurred at the A5199

Northampton Road / Brampton Lane priority junction involved vehicles turning right, or waiting to turn

right, at the junction from both the Welford Road and Brampton Lane arms.

4.7.9. Although there appears to be an apparent cluster of incidents at this location which could pose safety

concerns, it should be noted that this junction is to be reconfigured into a four arm roundabout as part

of the NWRR scheme. The reconfiguration of this junction will provide several safety benefits

compared to the existing arrangement (see paragraph 6.4.5 for details).


Figure 4-12 - PIC Plot B: Brampton Lane/Vyse Road/A508

4.7.10. Figure 4-12 shows the Brampton Lane / A508 Harborough Road / Vyse Road Roundabout junction

which is located to the east of the proposed NWRR scheme.

4.7.11. Figure 4-12 shows that a serious PIC occurred on the south-western section circulatory carriageway

of the roundabout. Further analysis revealed that this incident only involved a single party and was

due to driver error.


Figure 4-13 - PIC Plot C: Brampton Lane/A508/High Street

4.7.12. Figure 4-13 shows the Brampton Lane / A508 Harborough Road priority junction and the A508

Harborough Road / High Street priority junction which are located to the west of Pitsford village which

is located to the north east of the proposed NWRR scheme.

4.7.13. Figure 4-13 shows that four PICs, classified as serious to slight, occurred at this location with two

PICs occurring at each junction.

4.7.14. Further analysis of the PICs that occurred at the A508 Harborough Road / High Street priority junction

revealed no common themes between the two PICs with one PIC involving a pedestrian being run

over and the other PIC occurring due to driver behaviour as two vehicles collided trying to avoid a

vehicle pulling out of the High Street.

4.7.15. Further analysis of the PICs that occurred at the Brampton Lane / A508 Harborough Road priority

junction revealed that one of the PICs involved a vehicle waiting to turn right from A508 Harborough

road to Brampton Lane and the other involved a cyclist waiting to turn right from A508 Harborough

road to Brampton Lane.


Figure 4-14 - PIC Plot D: A508/A5076

4.7.16. Figure 4-14 shows PICs that occurred at and around the A508 Harborough Road / Holly Lodge Drive

signalised junction which is located to the east of the proposed NWRR scheme.

4.7.17. Figure 4-14 shows that three slight PICs have occurred in this area. Further analysis that two of the

three PICs involved vehicles that were turning right into A5076 Holly Lodge Drive whilst the other PIC

occurred between two vehicles in the left turn lane from A5076 Holly Lodge Drive.

Summary

4.7.18. The PIC analysis has revealed that there were a total of twelve incidents which occurred within the

area of influence of the proposed scheme between the period of 2014 to 2019. Of these incidents, ten

were classified as slight and two were serious.

4.7.19. The data suggests that there are no common patterns or trends in accidents, apart from those which

occurred at the A5199 Northampton Road / Brampton Lane / Welford Road priority junction. However,

it is noted that this junction is proposed to be reconfigured into a four arm roundabout to provide

access to the NWRR, with the reconfiguration anticipated to include associated safety benefits.

4.7.20. Notwithstanding the above, no locations are identified which would experience a change in their safe

operation. The new infrastructure proposed will be constructed to the required standards and will be

subject to road safety audits to ensure safety for all users.


5 DEVELOPMENT PROPOSALS

5.1 INTRODUCTION

5.1.1. This section of the report describes the different aspects of the proposed scheme, and describes the

related proposed development which provides context as to the reasons why the overall NWRR is

being proposed.

5.2 PROPOSED NORTH WEST RELIEF ROAD

5.2.1. The northern section of the NWRR (approximately 1.61km in length) is being delivered by NCC. The

remainder of the road (referred to the southern section) is to be delivered by the developer of the

Dallington Grange housing development which will be located to the south-west of the proposed

scheme.

5.2.2. The NWRR between the A428 Harlestone Road and the A5199 Welford Road is necessary to enable

and unlock the future development of 6,600 houses and more than 3,000 jobs in Northampton; as

stated in the NWRR’s Outline and Full Business Case5.

5.2.3. As noted in section 4.6 above, the existing traffic conditions on the local highway network experience

congestion in northern Northampton and nearby villages which currently suffer from high volumes of

traffic and associated disturbance. The NWRR will relieve existing pressures on the network, as well

as improving the quality of life for local residents, commuters and enhance the character of nearby

villages by redirecting traffic and reducing local congestion.

5.2.4. In addition, the NWRR will form part of a longer-term strategy to deliver a route from the A4500 near

Junction 16 of the M1 and the A43 north of Northampton, creating an orbital route option around

Northampton. Again, this has the aim of improving the quality of life for existing residents and

commuters as, once completed, less traffic should route through Northampton.

5.2.5. The full orbital route is illustrated on Figure 5-1 overleaf.

5 https://www.northamptonshire.gov.uk/councilservices/northamptonshire-highways/major-highway-projects/Documents/Major%20highways%20projects/300120%20NWRR%20Full%20Business%20Case%20minus%20App%20PDF%206.7MB.pdf

https://www.northamptonshire.gov.uk/councilservices/northamptonshire-highways/major-highway-projects/Documents/Major%20highways%20projects/300120%20NWRR%20Full%20Business%20Case%20minus%20App%20PDF%206.7MB.pdf




Figure 5-1 - Full Orbital Route Schematic

5.3 PROPOSED NEW ACCESS JUNCTIONS

5.3.1. The following new access junctions at the northern end of the proposed NWRR have been proposed

to connect it to the existing road network:

A: Sandy Lane / Northampton Road / NWRR Roundabout; and

B: Northampton Road / Welford Road / Brampton Lane Roundabout.

5.3.2. The layout and locations of these junctions along with the downgraded section of A5199 Northampton

Road are illustrated in Figure 5-2 (overleaf).


Figure 5-2 - Proposed NWRR Access Junctions and downgraded section of A5199

Northampton Road (known as Causeway Link)

A: SANDY LANE / NORTHAMPTON ROAD / NWRR ROUNDABOUT

5.3.3. A four-armed roundabout is proposed at the northern end of the NWRR to connect the NWRR to the

existing road network.

5.3.4. The proposed Sandy Lane / A5199 Northampton Road / NWRR Roundabout will be located

approximately 10m west of the River Nene and 20m south of the existing Sandy Lane Junction which

connects into the A5199 Northampton Road. The proposed roundabout will be on embankment up to

5m above surrounding ground levels.

5.3.5. The proposed roundabout will directly replace the existing priority junction that connects Sandy Lane

with the A5199 Northampton Road. The proposed Sandy Lane Roundabout will include four arms:

The northern arm will connect into the A5199 Northampton Road;

The eastern arm will connect into the proposed carriageway linking the proposed Sandy Lane

Roundabout with the proposed Brampton Lane Roundabout. This proposed carriageway will form

part of the A5199 Northampton Road;

The southern arm will connect into the proposed carriageway linking the proposed Sandy Lane

Roundabout with the Dallington Grange Roundabout; and


The western arm will connect into Sandy Lane.

5.3.6. Foot/cycleway provisions will be included on the western and northern arms of the roundabout to

ensure there is connectivity to existing NMU provisions. It is proposed to reserve the section of the

A5199 Northampton Road for NMU use only as part of the NWRR scheme which includes the closure

of this section of road to motorised traffic.

5.3.7. The proposed layout is illustrated in Drawing NWRR-WSP-SGN-0000-DR-CH-00004 P02, contained

within Appendix E and shown in Figure 5-3 later in this section.

Alterations to Existing A5199 Northampton Road

5.3.8. Traffic modelling undertaken shows that the existing river bridge on the A5199 Northampton Road

would not be suitable for the predicted traffic flows after opening of the NWRR and following

completion of local developments. Therefore, a short section of the A5199 Northampton Road,

approximately 250m in length (which includes the existing river bridge), will be permanently closed to

motorised vehicle use once the Proposed Scheme is operational.

5.3.9. This short section runs from west to east, starting at the Sandy Lane/A5199 Northampton Road

junction and ends at the Brampton Mill Equestrian Centre side road access. This short section of the

A5199 Northampton Road which is downgraded will remain in place and be open to NMUs and is

shown in Figure 5-2. This section of road will be known as the “Causeway Link”.

B: NORTHAMPTON ROAD / WELFORD ROAD / BRAMPTON LANE ROUNDABOUT

5.3.10. It is proposed that the existing A5199 Northampton Road / Brampton Lane / Welford Road three-

armed priority junction will be converted into a 4-armed roundabout. The proposed Brampton Lane

Roundabout will be located approximately 10m south-west of the Windhover Public House. The

proposed roundabout will be on embankment up to 2m above surrounding ground levels.

5.3.11. The proposed roundabout will directly replace the existing priority junction that connects Brampton

Lane with the A5199 Northampton Road / Welford Road. The proposed Brampton Lane Roundabout

will include four arms:

The northern arm will only provide access to existing residential properties and the Brampton Mill

Equestrian Centre and ensure there is connectivity to existing NMU provision such as Footpath

CC5 and the Brampton Valley Way;

The eastern arm will connect into Brampton Lane;

The southern arm will connect into the A5199 Welford Road; and

The western arm will connect into the proposed new section of the A5199 Northampton Road.

5.3.12. Foot/cycleway provisions will be included on the western, northern and eastern arms of the

roundabout to ensure there is connectivity to existing NMUs.

5.3.13. The proposed layout is illustrated in Drawing NWRR-WSP-SGN-0000-DR-CH-00005 P03, contained

within Appendix E and shown in Figure 5-4 later in this section.

5.4 DALLINGTON GRANGE DEVELOPMENT

5.4.1. Dallington Grange is the development that will be located to the south of the northern section of the

NWRR (the subject of this TA) and west of Kings Heath. Dallington Grange will comprise the

construction of around 3,000 residential dwellings, with a mix of private and affordable units. Dallington


Grange will also include 10ha of employment uses, two primary schools and some mixed-use areas,

with land reserved for a secondary school on previously undeveloped land.

5.4.2. The site will be accessed by various pedestrian, cyclist and vehicular accesses linking to the current

highway, footpath and cycle network. The northern section of the NWRR will provide the primary

vehicle and cyclist access to Dallington Grange from the north, whilst the southern section of the

NWRR will provide the primary vehicle and cyclist access to Dallington Grange from the south, via the

existing Harlestone Road / New Sandy Lane / York Way Roundabout.

5.4.3. The southern section of the NWRR (to be delivered by the developer of the Dallington Grange housing

development site) is approximately 2km (1¼ miles) in length, routing from the internal roundabout

with the northern section of the NWRR in a south-west alignment to join the York Way arm of the

existing Harlestone Road / New Sandy Lane / York Way Roundabout.

5.4.4. Appendix F contains the Illustrative Masterplan produced by Pegasus showing the proposals for the

site and the associated transport links. In accordance with the JCS, it is expected that the site will be

completed by 2026.

5.4.5. In November 2018, a resolution to grant planning permission was made for the Dallington Grange

development. This outline planning permission includes the southern section of the NWRR to be

delivered by the developer of the Dallington Grange housing development site.

5.5 PROPOSED CYCLE, WALKING AND HORSE RIDING FACILITIES

5.5.1. This section provides details of the walking, cycling and horse riding facilities that will be delivered as

part of the proposed scheme. Walkers, cyclists and horse riders are referred to as NMUs.

5.5.2. As stated earlier in this section of the report (see paragraph 5.3.8), a short section of the A5199

Northampton Road (known as the Causeway Link) will be permanently closed to motorised use once

the proposed scheme is operational.

5.5.3. Figure 5-2 (provided above) illustrates the short section of the A5199 Northampton Road that will be

permanently closed to motorised use, but will remain open to NMUs once the proposed scheme is

operational.

5.5.4. In addition to the above, a shared foot/cycle way will be provided from the Dallington Grange

Development to the Sandy Lane / Northampton Road / NWRR proposed roundabout via the western

side of the NWRR.

5.5.5. The proposed cycle, walking and horse riding facilities are illustrated in the General Arrangement

drawing contained within Appendix E.

SANDY LANE / NORTHAMPTON ROAD / NWRR ROUNDABOUT NMU FACILITIES

5.5.6. Figure 5-3 (overleaf) illustrates the NMU facilities provided at the proposed Sandy Lane / Northampton

Road / NWRR Roundabout. The drawing shows that foot / cycleway provisions will be included on the

southern, western and northern arms of the roundabout to ensure there is connectivity to existing and

proposed NMU provisions. Figure 5-3 shows that:

An informal pedestrian and cyclist crossing facility will be included on the Sandy Lane (western)

arm of the roundabout; and


A Toucan and a separate Pegasus crossing will be included on the A5199 Northampton Road

(northern) arms of the roundabout.

5.5.7. The proposed crossing facilities will ensure that there is connectivity to existing NMU user provision

from the roundabout and will provide connectivity to the Causeway Link.

Figure 5-3 - NMU facilities proposed at the Sandy Lane / Northampton Road / NWRR

Roundabout

NORTHAMPTON ROAD / WELFORD ROAD / BRAMPTON LANE ROUNDABOUT

5.5.8. Figure 5-4 (overleaf) illustrates the NMU facilities provided at the proposed Northampton Road /

Welford Road / Brampton Lane Roundabout. The drawing shows that foot / cycleway provisions will

be included on all arms of the roundabout to ensure there is connectivity to existing NMU provisions.

5.5.9. Figure 5-4 shows that the following will be provided:


A Toucan crossing on the western arm (A5199 Northampton Road) which will join a new footway

that will link to the NCR 6;

A shared use uncontrolled crossing on the northern arm (Causeway Link) of the roundabout which

will join a path that will link to the Brampton Valley Way;

A shared controlled crossing on the eastern arm (Brampton Lane) of the roundabout which will join

a path that will link to the Brampton Valley Way as well as connect to the shared foot / cycleway on

Welford Road; and

A shared use uncontrolled crossing on the southern arm (Welford Road) of the roundabout which

will also join a path that will link to the Brampton Valley Way.

5.5.10. The above measures will help maintain suitable and sufficient NMU access to and between the

Brampton Valley Way and NCR 6 and other existing Public Rights of Ways (PRoWs). The above

measure will also provide NMU access to the section of the A5199 Northampton Road that will be

permanently closed from motorised use but will remain in place and be open to NMUs once the

proposed scheme is operational.

Figure 5-4 - NMU facilities proposed at the Northampton Road / Welford Road / Brampton

Lane Roundabout


OTHER NMU FACILITIES

5.5.11. As stated above, Appendix E contains the General Arrangement drawings of the proposed scheme

which illustrate the shared 3m footway/cycleway that will be on the western side of the NWRR.

5.5.12. The following details a range of other NMU facilities, or facilities that will impact NMU usage, that are

either proposed as part of the proposed scheme or directly related to the proposed scheme:

Adequate street lighting will be installed at both the Sandy Lane / Northampton Road / NWRR and

the Northampton Road / Welford Road / Brampton Lane Proposed Roundabouts;

As part of the Dallington Grange development, public footpath HW44 will be diverted to route to

the existing bridge where the River Nene crosses the railway line rather than using the existing

level crossing, which will provide a safer crossing of the railway line; and

As part of the Dallington Grange scheme, bridleway HW6 is to be diverted and connected to the

wider bridleway network. The rerouted bridleway HW6 will link directly to the eastern arm of the

roundabout located in the Dallington Grange development which will in turn provide NMU access

to the proposed scheme.

WALKING, CYCLING AND HORSE RIDING ASSESSMENT REVIEW

5.5.13. It should be noted that the Walking, Cycling and Horse-Riding Assessment Review (WCHAR) process

has been applied throughout the design and development of the proposed scheme. This has been

with the purpose of facilitating the inclusion of walking, cycling and horse-riding modes of travel in the

highway scheme design process from the earliest stage, enabling the design team to identify

opportunities for improved facilities and integration with the local and national networks.

5.5.14. The WCHAR process is made up of two distinct parts. The first part is an assessment of the existing

situation, the Walking, Cycling & Horse-Riding Assessment, or Assessment Report. The second part

relates to an ongoing review of user opportunities throughout the design process, the Walking, Cycling

& Horse-Riding Review, or Review Report. The WCHAR process concludes prior to the

commencement of construction of a highway scheme.

5.5.15. The first part of the WCHAR has been completed and has identified a range of opportunities to

incorporate pedestrian, cyclist and horse-riding facilities into the scheme and the surrounding area.

These identified opportunities were presented to and considered by the wider design team throughout

the progression of the scheme design. This resulted in a number of these opportunities being

incorporated into the design of the proposed scheme (see the sections above).

5.5.16. It should be noted that the second part of the WCHAR process is an ongoing review of user

opportunities throughout the design process and may therefore identify additional NMU facilities to

include in the proposed scheme if deemed appropriate.


6 TRAFFIC IMPACT ASSESSMENT

6.1 INTRODUCTION

6.1.1. This section of the report assesses the impact of the proposed scheme on the operation of the local

highway network. It describes the transport modelling approach, development assumptions, and

modelling results, thereby establishing the traffic impact of the scheme. This section also assesses

whether the proposed scheme could exacerbate any existing Personal Injury Collision (PIC) patterns.

Finally, this section of the report uses the results from the local highway impact assessment to build

upon the wider benefits of the proposed scheme.

6.1.2. Following the assessment of the local highway network, individual junction modelling has been

undertaken in Chapter 7 of this report. The mitigation measures identified in support of the proposed

scheme are detailed in Chapter 8. Finally, Chapter 9 sets out the Monitor and Manage Strategy

proposed as part of the scheme.

6.2 MODELLING APPROACH

6.2.1. As agreed with NH’s Development Control Team, the Northamptonshire Strategic Transport Model

(NSTM) has been used as the basis to assess the impact that the proposed scheme is likely to have

on the operation of the surrounding highway network.

6.2.2. It should be noted that a more localised version of the NSTM which models traffic flows on the highway

network in the Area of Influence (AOI) of the proposed NWRR scheme has been developed to assess

the proposed scheme. This has been agreed with NH’s Development Control Team in support of the

previous TA dated May 2019 and therefore deemed appropriate to use for this assessment.

6.2.3. The following modelling scenarios, which were agreed with NH’s Development Control Team, have

been assessed in this TA for both morning and evening peaks:

2015 Base;

2021 DM - Do Minimum (without ‘proposed scheme and also without NWRR Southern Section’);

2021 DS - Do Something (with ‘proposed scheme and also with NWRR Southern Section’);

2031 DM - Do Minimum (without ‘proposed scheme and also without NWRR Southern Section’);

and

2031 DS - Do Something (with ‘proposed scheme and also with NWRR Southern Section’).

6.2.4. The Do Minimum (DM) modelling scenarios includes the forecast additional traffic associated with the

Dallington Grange development along with other committed developments.

6.2.5. The Do Something (DS) modelling scenarios contain everything included in the Do Minimum

scenarios but also the entire extent of the NWRR.

MODELLING ASSUMPTIONS

6.2.6. For the purpose of this TA, it has been assumed that the proposed scheme would open in 2021 and

the future assessment year would be ten years after scheme opening (2031).

6.2.7. It should be noted that the Sandy Lane Relief Road (Phase 2) is also expected to be operational in

2021 and has therefore been included in both future year modelling scenarios. However, if the scheme

was not operational by 2021, it would more than likely reduce the traffic flows that use the NWRR in


the scheme’s opening year and would therefore result in a scenario with a lower impact. From a traffic

impact point of view, using the current NSTM model assumption would therefore provide a more robust

assessment, as it considers a worst case. It should also be noted that this approach is in line with

what is included in the proposed scheme’s Full Business Case that was submitted in January 2020.

UPDATED NSTM

6.2.8. Following the submission of the original TA (May 2019) and subsequent TAA (September 2019),

concerns were raised regarding how representative the future year traffic flows extracted from NSTM

were likely to be of the traffic conditions experienced in reality. As explained in paragraph 4.6.2, the

NSTM base localised model has since been recalibrated and validated with traffic counts undertaken

in May 2019 for an average weekday at several locations in proximity to the proposed scheme. The

traffic counts derived from the 2019 surveys were brought back to a 2015 level using TEMPro growth

rates as the NSTM was originally developed for a 2015 base year.

6.2.9. The locations where the May 2019 traffic surveys were undertaken include the following sites:

A5199 Northampton Road / Sandy Lane Priority Junction;

A5199 Northampton Road / Brampton Lane / Welford Road Priority Junction;

A508 Harborough Road / Brampton Lane / Vyse Road Roundabout;

A508 Harborough Road / Brampton Lane Priority Junction;


A428 Harlestone Road / New Sandy Lane / York Way Roundabout;

A508 Harborough Road / A5076 Holly Lodge Drive Signalised Junction; and

New Sandy Lane / Berrywood Road / Roman Road Double Mini Roundabout.

6.2.10. The NSTM model is validated entirely in line with TAG6 guidance against a broad basket of observed

traffic and journey time data. However, it is also the case that at the local level, there are individual

locations where there are differences between modelled and observed data that need to be

addressed. At these locations, localised adjustment factors have been applied to account for the

differences in the modelled and observed flows in regard to individual junction modelling (refer to

paragraph 7.2.1 for further details) to provide a more robust assessment.

6.2.11. In addition to the above, the NSTM has been updated following revisions to some of the major

committed developments which are likely to have an impact on the scheme. These committed

developments are coded into the model for the future year scenarios (2021 and 2031) as they have

an impact on the flows of the proposed scheme. The analysis of the revised NSTM is presented in

later sections of this report.

6 TAG is the online transport analysis guidance provided by the Department for Transport (DfT) that provides information on the role of transport modelling and appraisal. TAG provides guidance by which a strategic transport model should be validated to prove that it is fit for purpose to assess a proposed scheme.


6.2.12. It should be noted that the traffic flows from the previous TA (May 2019) have been compared against

the latest updated flows to provide a more robust assessment at specific junctions (detailed in Chapter

7).

6.3 LOCAL HIGHWAY IMPACT ASSESSMENT

6.3.1. This section presents the results of the proposed scheme assessment which has been undertaken

using the NSTM. Results for the future assessment years of 2021 and 2031 have been extracted

from the NSTM for both the AM and PM peak hours.

6.3.2. For this section of the report, the Do Minimum scenario has been referred to as the “Without Scheme”

scenario whilst the Do Something scenario has been referred to as the “With Scheme” scenario.

6.3.3. Analysis of the NSTM results was initially undertaken to understand the impact that the proposed

scheme would have on the wider Northampton highway network (the proposed scheme’s overall

impact). The results extracted and analysed included the following parameters:

Flow Difference;

Junction Volume/ Capacity Ratio (V / C); and

Junction Delay.

FLOW DIFFERENCE

6.3.4. This section includes flow difference plots illustrating the beneficial impacts on the network of the With

(NWRR) Scheme scenario against the Without (NWRR) Scheme scenario. As the only difference

between the two scenarios is the presence of the scheme (in the With Scheme scenario), it is

reasonable to assume that any re-routeing is due to the scheme.

6.3.5. Flow difference plots are presented for the 2031 AM and PM peak hours in Figure 6-1 and Figure 6-

2 (overleaf). These display a graphical comparison between the 2031 With Scheme scenario and

2031 Without Scheme scenario for the AM and PM peak hours, respectively. The plots display the

change in traffic flow in PCUs per hour with the level of change being indicated using bandwidths. As

classified in the legend, green indicates an increase in flow whilst blue indicates a decrease in flow.

6.3.6. The 2021 With Scheme scenario and 2021 Without Scheme scenario flow difference plots can be

found in Appendix G. In 2021, the primary observation is that, even without the delivery of the full

Dallington Grange development, it is apparent that the NWRR will provide relief on the corridors

identified as already experiencing a degree of congestion in 2015 (see section 4.6). This includes the

east-west Mill Lane Corridor and the north-south Harlestone Road and Lumbertubs Way Corridors. It

is therefore apparent that providing the NWRR will alleviate existing issues with traffic having to travel

on Northampton’s primary radial and orbital corridors.


Figure 6-1 – 2031 AM Peak Flow Difference Plot (With Scheme less Without Scheme)


Figure 6-2 - 2031 PM Peak Flow Difference Plot (With Scheme less Without Scheme)


6.3.7. Figure 6-1 and Figure 6-2 above indicate that the proposed scheme delivers two key benefits. Firstly,

several corridors show a reduction in traffic against even the 2015 baseline. These locations include:

A43 Lumbertubs Way;



A4500 Weedon Road;


Harlestone Road (The Bramptons) and

Mill Lane.

6.3.8. The reduction of traffic on Mill Lane and Harlestone Road (The Bramptons) subsequently

demonstrates the scheme’s benefits in relieving congestion from existing orbital corridors which are

either not fit for purpose (Harlestone Road through the small towns of the Bramptons) or approaching

capacity at access/egress junctions (Mill Lane; see Figure 4-7 and Figure 4-8). As such, there is a

strong benefit to delivering the scheme prior to considering its additional benefits in reducing traffic

produced by the Dallington Grange development.

6.3.9. These observations, in conjunction with reductions in traffic on many other, secondary and/or estate

roads, suggests that the proposed scheme is likely to:

Reduce the unintended vehicular traffic that currently routes through the Brampton villages and

some residential areas of Kingsthorpe; and

Reduce the congestion at roads and junctions on key routes into town; such as on Mill Lane and

the A508 Harborough.

6.3.10. Figure 6-1 and Figure 6-2 also shows the considerable benefits of delivering the NWRR in

conjunction with the Dallington Grange development. This can be seen by a forecast reduction in

traffic flow in both the modelled AM and PM peak time periods on:

Section of Harlestone Road West of the New Sandy Lane Roundabout;

A508 Kingsthorpe Road / Harborough Road7;




Eastern Avenue.

6.3.11. The reduction of traffic on these corridors between the 2031 Without Scheme and With Scheme

scenarios show the importance of the NWRR in allowing traffic to and from Dallington Grange without

having to travel through Northampton Town centre and/or use already congested east-west corridors

7 With the introduction of the NWRR scheme, it is noted that there is a reduction of traffic along this corridor which in turn results in the reduction of delays at the Cock Hotel junctions. This delay reduction includes the intersection outside the Cock Hotel where Mill Lane and the A5095 junction cross the A508. Without the NWRR, this junction is a key access to the Dallington Grange development, as well as a key artery for north-south movements into Northampton.


to reach locations beyond the centre. This reduction in traffic will prevent excessive congestion and

subsequent issues with delay, pollution, noise and severance.

6.3.12. Figure 6-1 and Figure 6-2 show that the largest forecast increase in traffic flows with the proposed

scheme is along Brampton Lane, New Sandy Lane and the NWRR. In addition, they show that roads

routing through the villages of Moulton and Boughton (such as Vyse Road, Moulton Lane, Boughton

Road and West Street) are forecast to experience an increase in traffic flows with the proposed

scheme as it is forecast that vehicles will reroute along these roads when accessing and egressing

the NWRR. Key junctions which experience congestion as a result of the proposed scheme will be

assessed in Chapter 7 of this report.

6.3.13. Beyond the locations set out in the preceding paragraph, however, it is evident that the impact of the

NWRR overall is highly beneficial in both reducing existing traffic congestion and delay on the network

and in distributing traffic from Dallington Grange and other local/regional development sites in a way

that doesn’t overwhelm Northampton’s existing corridors. A more detailed analysis of the changes in

flow and subsequent benefits realised can be found in Section 6.5below.

JUNCTION VOLUME/ CAPACITY RATIO

6.3.14. As mentioned in paragraph 4.6.9, the Volume / Capacity Ratio (V/C) is used as an indicator of

congestion at a junction. Junctions which experience a V/C of greater than 85%, will begin to

experience increased delay and are likely to be affected by operational constraints.

6.3.15. V/C percentages are presented for junctions within the vicinity of the proposed NWRR location. The

congestion at the junctions have been identified by classifying the V/C ratios into five categories

mentioned below. The V/C ratios used for this analysis are the average turn V/C ratios at the junctions.

Category A: V/C ≥ 100% Ratio - Heavily congested junctions, shown in red dots;

Category B: 85% < V/C ≤100% - Congested junctions, shown in orange dots;

Category C: 75% < V/C ≤ 85% - Junctions approaching congestion, shown in yellow dots;

Category D: 50% < V/C ≤ 75%- Uncongested junctions, shown with small green dots; and

Category E: V/C < 50% - Uncongested junctions, shown with points.

6.3.16. It should be noted however that within NSTM, a V/C ratio is calculated for each permitted turn at a

junction. The average V/C value at each junction is used in this analysis. As the average value is

used, it can be unduly influenced, by turns with much lower and higher V/C. Additionally, it does not

consider tidal flow, where for example movements towards the town centre might be higher in the

morning peak hour than later in the day, and vice-versa. In operational terms, if any movement at a

junction is approaching capacity, queues and delays are likely to form, but this may not be clear from

V/C plots as these are average across the junction and not shown by movement.

6.3.17. Nonetheless, V/C plots form a useful comparative overview between scenarios. The 2021 With

Scheme and Without Scheme Junction V/C plots for both time periods are located in Appendix G.

6.3.18. A comparison of the 2031 With Scheme scenario and 2031 Without Scheme scenario plots for both

peak periods are shown in Figure 6-3 to Figure 6-6 below.


Figure 6-3 – 2031 AM Without Scheme Junction Volume/ Capacity Ratio


Figure 6-4 - 2031 PM Without Scheme Junction Volume/ Capacity Ratio


Figure 6-5 - 2031 AM With Scheme Junction Volume/ Capacity Ratio


Figure 6-6 – 2031 PM With Scheme Junction Volume/ Capacity Ratio


6.3.19. Figure 6-3 to Figure 6-6 show a reduction in V/C on a number of junctions in the With Scheme

Scenario in comparison to the Without Scheme scenarios. This includes the A508 and the Harlestone

Road corridors in addition to the Mill Lane east-west route. This demonstrates that the scheme’s

delivery alleviates the volume of traffic passing through these locations, in turn enabling more efficient

operation with less delay; as well as providing reserve capacity for any future growth in the town.

6.3.20. Table 6-1 below summarises key junctions in the study area which experience minimal or positive

impacts in regard to their operational capacity in the With Scheme scenario. The bandwidths are

classified in paragraph 6.3.15 above.

Table 6-1 - 2031 Junctions Volume / Capacity Category (Minimal or Positive Impact)

2031 AM Peak 2031 PM Peak

Junction Without Scheme

With Scheme

Without Scheme

With Scheme

Mill Lane / Nene Way D D D D

Mill Lane / Woodside Way D D D D

A4500 Weedon Road / Rosebery Avenue D D C C

A428 Harlestone Road / Bants Lane / Mill Lane D D D D

Mill Lane / Dallington Grange Access Junction D D D D

Mill Lane / Kingswell Road B C C D

6.3.21. As shown in Table 6-1 above, the With Scheme scenario results show that the impact on Mill Lane is

relatively minimal. The junctions with Nene Way and Woodside Way both remain with a high capacity

available (Band D), whilst the access junction is also projected to flow smoothly (Band D). The

Weedon Road/Rosebery Avenue junction is also unaffected, remaining at existing levels of

congestion. The notable change is at Mill Lane / Kingswell Road where V/C moves down a congestion

band, from B-C in the AM Peak and C-D in the PM peak, giving the junction some headway before

risking going over-capacity in either period.

6.3.22. Table 6-2 below summaries the key junctions which experience negative impacts in regard to their

operational capacity in the With Scheme scenario. These junctions become more congested as they

are located on routes where there is a forecast increase in traffic flows as a result of the NWRR (as

shown on the flow difference plots above).The bandwidths are classified in paragraph 6.3.15 above.

Table 6-2 – 2031 Junction Volume / Capacity Category (Negative Impact)



With Scheme

Without Scheme

With Scheme


C C D B

A508 Harborough Road / Brampton Lane Priority Junction; D B C C




With Scheme

Without Scheme

With Scheme

A508 Harborough Road / Brampton Lane / Vyse Road Roundabout;

E C E D

A508 Harborough Road / A5076 Holly Lodge Drive Signalised Junction;

D D D D

A5199 Northampton Road / Brampton Lane / Welford Road Priority Junction (existing and proposed);

E C E C

A5199 Northampton Road / Sandy Lane Priority Junction (existing and proposed);

E D E D

A428 Harlestone Road / New Sandy Lane / York Way Roundabout; and

E C E C

New Sandy Lane / Berrywood Road / Roman Road Double Mini Roundabout.

D D D D

6.3.23. As agreed through the scoping process, the junctions presented in Table 6-2 above have been taken

forward for individual junction capacity assessments to understand what the impact the proposed

scheme will have at these junctions. The results of the junction capacity analysis are presented in

Chapter 7 of this report.

JUNCTION DELAY

6.3.24. This section provides details of the modelled delay at junctions surrounding the proposed scheme.

The 2021 With Scheme and Without Scheme junction delay plots for both time periods are located in

Appendix G.

6.3.25. The modelled delay at the junctions are compared for the 2031 Without Scheme scenario results with

the 2031 With Scheme scenario results for both the AM and PM peak hours.

6.3.26. Figure 6-7 to Figure 6-10 (overleaf) show the modelled average delay in seconds experienced per

PCU at junctions located within the vicinity of the proposed scheme. The level of delay is indicated by

the size of the points identifying the junction, as classified in the legend.


Figure 6-7 - 2031 AM Without Scheme Junction Delay


Figure 6-8 - 2031 AM With Scheme Junction Delay


Figure 6-9 - 2031 PM Without Scheme Junction Delay


Figure 6-10 - 2031 PM With Scheme Junction Delay


6.3.27. Figure 6-7 to Figure 6-10 show that the scheme delivers marked reductions in delay at junctions on

the corridors towards Northampton Town Centre. The most notable changes are on Harborough

Road, Harlestone Road and Main Road. The orbital links closer to the city centre also show marked

relief, including Mill Lane and Spencer Bridge Road, as well as some relief of junctions on St James

Road.

6.3.28. Two junctions in the study area show marked increased AM peak hour delay in a With Scheme

scenario, as well as slight increases in the PM peak. These are:

Northampton Road / Brampton Lane / Welford Road / NWRR; and

Harlestone Road / NWRR / Harlestone Road / New Sandy Lane.

6.3.29. There are also small increases in delay in both directions on Sandy Lane and New Sandy Lane, as

well as Brampton Lane and Vyse Lane.

6.3.30. The delay in seconds at the junctions have been identified and classified into seven categories

mentioned below:

Category A: Delay > 300s;

Category B: 180s < Delay ≤ 300s;

Category C: 120s < Delay≤ 180s;

Category D: 90s < Delay ≤ 180s;

Category E: 60s < Delay ≤ 90s;

Category F: 30s < Delay ≤ 60s; and

Category G: Delay ≤ 30s.

6.3.31. Table 6-3 below presents junctions which are modelled to experience the most significant reductions

in delay in the 2031 With Scheme scenario when compared to the Without Scheme scenario

throughout the NSTM modelled area.

Table 6-3 - 2031 With Scheme and Without Junctions Delay Category (Modelled Area)



With Scheme

Without Scheme

With Scheme

Berrywood / Southfield Road B D G F

A5199 Welford Road / Back Lane G G G G

A508 Harborough Road / High Street (South of Boughton Green Road)

D F G G

A428 Harlestone Road / Lodge Way / Firsview Drive D E E F

A508 Harborough Road / A5095 Kingsthorpe Road / Mill Lane (The Cock Hotel Junction)

E E B E

Tollgate Way / Main Road E F G G

6.3.32. Table 6-3 above shows that the largest benefits are realised at the A508 / A5095 / Mill Lane junction

in the PM peak, where east-west flows intersect with traffic travelling north-south, as well as

movements south-east to north-west. By relieving the need to travel into Town on the A508 to travel


west, or to use Mill Lane for that purpose, the NWRR removes several minutes of delay from this

intersection. The next largest benefits are realised at the Berrywood / Southfield road intersection in

west Northampton, one of the key roads used for east-west trips. This junction also reduces delay by

several minutes from the approaches to the intersection.

6.3.33. The A508 Harborough Road / High Street (South of Boughton Green Road) and Tollgate Way / Main

Road both show 30-60 second delay reductions in the AM peak, whilst the A428 Harlestone Road /

Lodge Way / Firsview Drive shows benefits in both peaks.

6.3.34. Therefore, whilst outside of the core study area detailed below, it’s evident that the NWRR can reduce

delay and congestion from several key routes into Northampton, as well as on both primary and east-

west movements.

6.3.35. Table 6-4 below presents the changes in modelled junction delay category for the 2031 forecast year

Without Scheme and With Scheme scenarios for both the AM and PM peak at selected key junctions

surrounding the proposed scheme.

Table 6-4 - 2031 With Scheme and Without Scheme Junction Delay Category for Key

Junctions Identified



With Scheme

Without Scheme

With Scheme

New Sandy Lane / Harlestone Road / York Way Roundabout

G F G G

A5199 Northampton Road / Sandy Lane Priority Junction

G G F G

A5199 Northampton Road / Brampton Lane Priority Junction

F E E E

Brampton Lane / Home Farm Drive Roundabout G G G G

Brampton Lane / A508 Harborough Road / Vyse Road Roundabout

G G G F

A5076 Holly Lodge Drive / A508 Harborough Road Signalised Junction

F G G G

Brampton Lane / A508 Harborough Road Priority Junction

F E E E

A508 Harborough Road / Pitsford High Street Priority Junction

F E G F

6.3.36. As shown in the table and plots above, A508 Harborough Road / High Street priority junction forecast

to experience increases delays in the With Scheme scenario compared to the Without Scheme

scenario for both time periods.

6.3.37. The New Sandy Lane / Harlestone Road / York Way roundabout and A5199 Northampton Road /

Brampton Lane priority junction are forecast to experience increases in delay the With Scheme

scenario compared to the Without Scheme scenario only in the AM peak. There is also a slight


increase in delay at Brampton Lane / A508 Harborough Road / Vyse Road round in the PM peak hour

only.

6.3.38. There is also a slight reduction in delay at the A5076 Holly Lodge Drive / A508 Harborough Road

signalised junction.

6.3.39. As expected, the junctions that show an increase in modelled delay by change of category correspond

with the junctions that have the largest increases in modelled V/C, along routes where there is a

forecast increase in traffic flow in the With Scheme scenario compared to the Without Scheme

scenario.

6.4 IMPACT ON PERSONAL INJURY COLLISIONS

6.4.1. As set out above, it is unlikely that the traffic forecast to re-route due to the proposed scheme will lead

to a significant increase in PICs occurring on the surrounding highway network.

6.4.2. Firstly, analysis of the PICs that have occurred at selected key locations on the surrounding highway

network between 26/07/2014 to 17/06/2018 revealed that there were only two sites where more than

one PIC occurred within close proximity of one another and were attributable to common causes.

These occurred at the following junctions:

A5199 Northampton Road / Brampton Lane Priority Junction; and

A508 Harborough Road / A5076 Holly Lodge Drive Signalised Junction.

A5199 Northampton Road / Brampton Lane Priority Junction

6.4.3. Three of the PICs that occurred at the A5199 Northampton Road / Brampton Lane priority junction

involved vehicles turning right, or waiting to turn right, at the junction from both the Welford Road and

Brampton Lane arms.

6.4.4. The proposed scheme involves reconfiguring this junction from a priority junction into a roundabout

junction (see Section 5.3 for further details), and therefore any site-specific geometric characteristics

that could have contributed to these accidents would no longer be present.

6.4.5. It is also noted that the Design Manual for Roads and Bridges’ (DMRB’s) Advice Note CD 116

“Geometric Design of Roundabouts” document8 states that roundabouts offer safety benefits,

especially when travelling along high speed roads such as dual carriageways. The provision of a

roundabout, especially those equipped with ‘Reduce Speed Now’ signs and/or transverse yellow bar

markings can have the ability to “reduce rear shunt and overshoot accidents by helping to alert the

driver to the presence of the roundabout” as speeds can often be reduced in ample time.

8 Design Manual for Roads and Bridges: CD 116 Geometric Design for Roundabouts. Accessed online via: http://origin.standardsforhighways.co.uk/ha/standards/dmrb/vol6/section2/CD%20116%20revision%201%20Geometric%20design%20of%20roundabouts-web.pdf

http://origin.standardsforhighways.co.uk/ha/standards/dmrb/vol6/section2/CD%20116%20revision%201%20Geometric%20design%20of%20roundabouts-web.pdf

http://origin.standardsforhighways.co.uk/ha/standards/dmrb/vol6/section2/CD%20116%20revision%201%20Geometric%20design%20of%20roundabouts-web.pdf


A508 Harborough Road / A5076 Holly Lodge Drive Signalised Junction

6.4.6. Further analysis of the PICs that occurred at the A508 Harborough Road / A5076 Holly Lodge Drive

Signalised Junction revealed that two of the three PICs involved vehicles that were turning right into

A5076 Holly Lodge Drive whilst the other PIC occurred between two vehicles in the left turn lane from

A5076 Holly Lodge Drive.

6.4.7. As only two of the three PICs that occurred at the A508 Harborough Road / A5076 Holly Lodge Drive

Signalised Junction are attributable to a common cause and these two PICs occurred nearly two years

apart from one another, these do not form a pattern. There is therefore no pattern of PICs which could

be exacerbated by changes in traffic at the junction related to the proposed scheme.

6.5 WIDER BENEFITS OF NWRR SCHEME

6.5.1. The results from the local highway impact assessment (presented in section 6.3 above) indicated that

the proposed scheme attracts traffic that would have previously used the parallel / alternative routes.

The forecast reduction in traffic flows suggested that the proposed scheme would:

Reduce routing through traffic through the Brampton villages and some residential areas of

Kingsthorpe; and

Reduce the congestion at roads and junctions on key routes into and throughout the town.

6.5.2. This section of the report builds upon the wider benefits of the proposed scheme as they are key to

demonstrating that the scheme provides a positive outcome on balance for the highway network.

STRONG BUSINESS CASE

6.5.3. The Full Business Case9 (FBC) for the NWRR presents the needs for the scheme and has been critical

to securing funding. The FBC is demonstrated through the production of a number of cases including:

The Strategic Case which assesses the need for investment for the NWRR;

The Economic Case which assesses the impacts of the NWRR and the Value for Money (VfM) to

justify investment;

The Financial Case to determine the affordability of delivering the scheme;

The Commercial Case which provides evidence on the commercial viability of the NWRR; and

The Management Case to assess the deliverability of the proposed NWRR.

6.5.4. The Strategic Case is particularly relevant to the transport impact of the scheme as it sets the scheme

in context within the wider road network, the various developments and local, regional and national

objectives.

6.5.5. The Strategic Case demonstrates there is a need for appropriate infrastructure to provide additional

capacity on the transport network to support housing growth targets. This additional housing will add

9 WSP: Northampton North West Relief Road Full Business Case (January 2020). Accessed online via: https://www.northamptonshire.gov.uk/councilservices/northamptonshire-highways/major-highway-projects/Documents/Major%20highways%20projects/300120%20NWRR%20Full%20Business%20Case%20minus%20App%20PDF%206.7MB.pdf





demand to the existing highway infrastructure, therefore increasing journey times, congestion and

potentially creating adverse impacts on journey time reliability. The case concludes that there is a

need for the NWRR to support housing growth by providing additional highway capacity to the network.

Specifically, the NWRR would support local developments by increasing highway capacity in the local

area and providing a new east-west link between the A428 and A5199.

6.5.6. Modelling outputs indicate trips with an origin or destination at Buckton Fields and Dallington Grange

would use the NWRR, providing an essential east-west link in the north-west of Northampton to

support these developments. Without the NWRR, traffic arising from the developments would fully

load onto the existing road network, such as Mill Lane and the Cock Hotel junctions; causing

congestion and restricting the full development potential of the Dallington Grange site.

6.5.7. The modelling highlights that, without the NWRR, traffic loading onto the Dallington Grange

development is via Harlestone Road and Mill Lane. However, with the NWRR scheme going ahead,

traffic loading from Dallington Grange would be more evenly distributed. The modelling demonstrates

the relief road takes a substantial amount of traffic flows from Dallington Grange, which relieves

pressure on the existing network, due to a reduced amount of development traffic loading onto Mill

Lane and Harlestone Road.

6.5.8. In addition, modelling outputs also produced volume capacity ratios for the highway network at

junctions should Dallington Grange be delivered with and without the NWRR. In comparison, the

modelling outputs highlight that there is a greater likelihood of congestion on Harlestone Road and

Mill Lane should the NWRR not be delivered.

6.5.9. The Economic Case sets out the value for money for the scheme based on the Benefit/Cost Ratio

(BCR). The BCR is used in analysis to summarise the overall relationship between the relative costs

and benefits of a proposed project. The Economic Case for the scheme revealed that the overall travel

time savings resulted in a high BCR of 7:1. This demonstrates that the savings, predominantly to travel

time, outweigh the cost of delivering the scheme by 7 times, a very high return for a transport scheme.

The BCR calculation also includes benefits associated with accident reductions and severity,

greenhouse gases, noise and air quality.

6.5.10. To summarise, the delivery of the relief road would add additional highway capacity to the local

highway network and contribute towards alleviating the growing pressures on the network, to support

a reduction in journey times and emissions. If nothing is done, housing and employment growth will

continue to add to congestion; whereas the relief road will enhance connectivity and capacity. The

NWRR will promote economic growth by providing greater connectivity to the Strategic Road Network

(SRN) to support access to jobs and provide growth for businesses in the north-west of Northampton.

TRAFFIC BENEFITS

6.5.11. The NSTM is validated in line with TAG guidance against a broad range of observed traffic and journey

time data. It is therefore valid to use the NSTM flows for consideration of the wider benefits of the

scheme. It should be noted that the Do Minimum scenario excludes the NWRR but includes the

Dallington Grange development, whilst the Do Something scenario includes both NWRR and the

Dallington Grange development.

6.5.12. Plots are shown for the 2021 and 2031 future year scenarios in both the AM and PM peak periods

contained within Appendix G.


6.5.13. Figure 6-1 and Figure 6-2 (presented above in this chapter) shows the flow difference plots between

the 2031 Do Something and 2031 Do Minimum scenarios. This provides an illustration of the wider

benefits of the scheme which extend across the whole of Northampton Town. Some specific links

have been drawn from the plots to illustrate the wider benefits of the proposed scheme as shown in

Table 6-5 below.


Table 6-5 -Wider Traffic Benefits of the NWRR on Selected Links using NSTM flows

Location Description

Peak Hour

2021 Two- Way Flow 2031 Two-Way Flow

Without NWRR

With NWRR

% Change Without NWRR

With NWRR

% Change

Harlestone Road West of the New Sandy Lane

AM 1826 1025 -44% 1997 1550 -22%

PM 1848 1033 -44% 1974 1342 2%

Harlestone Road (between Lower Harlestone and the Bramptons)

AM 1197 495 -59% 1420 962 -32%

PM 1386 571 -59% 1468 941 -36%

Harlestone Road (through the Bramptons)

AM 611 199 -68% 729 575 -21%

PM 667 206 -69% 794 536 -33%

Mill Lane (West of the Harborough Road)

AM 2100 1816 -14% 2448 2196 -10%

PM 2038 1720 -16% 2107 2090 -1%

Harborough Road (North of Boughton Green Road)

AM 1178 1107 -6% 1166 997 -15%

PM 1281 1160 -9% 1469 1152 -22%

Harlestone Road (at Dallington Cemetery)

AM 1063 1269 19% 1722 1663 -3%

PM 976 1155 18% 1462 1441 -1%

Eastern Avenue (North of Kingsland Avenue)

AM 1104 939 -15% 1397 1061 -24%

PM 1097 846 -23% 1399 1075 -23%

6.5.14. Table 6-5 shows that the primary corridor to benefit from the NWRR is Harlestone Road, where there

are marked decreases in flow in compared to without the scheme. The Eastern Avenue corridor also

shows a reduction in traffic with the NWRR in place, although to a lesser degree than the change

observed on Harlestone Road.

6.5.15. The 2021 scenario shows an increase in traffic with the NWRR on the Harborough Road corridor; due

to the road feeding into the NWRR. In 2031 however, this corridor shows a decrease in traffic with the

NWRR, as without the scheme the corridor takes more development traffic compared to 2021.

OVERALL BENEFIT

6.5.16. Throughout this TA, it has been understood that the scheme has been designed with the aim of

achieving the optimum balance between wider benefits and local impacts and that the scheme has an

overall benefit. The locations selected above provide an indication of the benefits on some of the more

significant links, but other links around these will also experience changes to flows and travel patterns.

These changes can be seen on the plots contained in Appendix G.

6.5.17. However, the economic assessment included in the Business Case gives the best indication of the

overall effect on the network. The overall travel time savings result in a high Benefit/Cost Ratio (BCR)

of 7:1 which demonstrates that the savings, predominantly to travel time, outweigh the cost of

delivering the scheme by 7 times, a very high return for a transport scheme. The BCR calculation also


includes benefits associated with accident reductions and severity, greenhouse gases, noise and air

quality.

6.5.18. Another benefit is the additional resilience provided by this extra infrastructure. It is inevitable that

network disruption will occur from time to time, either due to planned roadworks, accidents or other

foreseen and unforeseen events. The NWRR therefore provides high quality additional infrastructure

to NCC’s highway portfolio, giving additional options and flexibility should it be required.

6.5.19. The NWRR will also promote economic growth and regeneration proposals in Northampton town

centre. Key strategic and policy documents (outlined in Chapter 3) set out the desire to underpin

Northampton as the key regional centre by increasing retail and employment floorspace. These growth

proposals for the town centre are forecast to generate additional traffic into the town. The NWRR

provides the opportunity to facilitate these additional vehicles, to support journey times and congestion

not only in the north-west, but also on the highway network in the town centre. This enhanced

connectivity would contribute to encouraging businesses to invest and locate in Northampton,

supporting Policy N1 ‘The Regeneration of Northampton’ within the West Northamptonshire Joint Core

Strategy. The growth of the local economy would also contribute towards further employment and

education opportunities, this along with increased accessibility, would promote the reduction in

unemployment and deprivation within areas of Northampton.

6.5.20. The scheme would also promote an improvement in the quality of life for Northamptonshire residents,

as by providing additional highway capacity through the scheme, capacity is released on existing

routes. This release of capacity will serve to encourage more active travel (cycling and walking trips).

Additionally, significant attention to sustainable modes has been included in the scheme design.

6.6 SUMMARY

6.6.1. This Chapter has assessed the impact of the proposed scheme on the operation of the local highway

network by comparing the future traffic conditions with and without the proposed scheme. The scheme

provides large benefits to the residents of Northampton by decreasing congestion against current

conditions, reducing unintended vehicular traffic through villages, providing capacity for further growth

and by providing an alternative access/egress route for the Dallington Grange development which

would otherwise be focused on the already congested Mill Lane.

6.6.2. The primary locations where benefits can be observed are:

Harlestone Road and A508 Harborough Road where the scheme reduces the number of trips

travelling on the radial corridor to travel east-west via connections to Mill Lane or Spencer Bridge

Road, both of which also show reductions in traffic flow with scheme;

There is also a concurrent reduction in congestion and delay at the intersections of the above

roads, such as The Cock Hotel junction.

Eastern Avenue and Lumbertubs way, which both show reductions in traffic in the With Scheme

scenario due to their need to relieve the core A508 being reduced.

Harlestone Road (through the Bramptons) which was previously being used as a rat-run avoiding

congestion on the aforementioned Mill Lane/Spencer Bridge routes.

6.6.3. All of these corridors show substantial reduction in traffic, thereby reducing congestion, traffic delay,

pollution and severance in the long term in comparison to a scenario without the NWRR and/or present

traffic conditions.


6.6.4. The results from the local highway impact assessments identified increases in traffic flows along

Brampton Lane and New Sandy Lane, as well as the roads routing through the villages of Moulton

and Boughton (such as Vyse Road, Moulton Lane, Boughton Road and West Street) as a result of the

proposed scheme. As expected, it is forecasted that vehicles will reroute along these roads / junctions

in order to access and egress the NWRR. Key junctions which experience congestion as a result of

the proposed scheme are assessed in Chapter 7 of this report.

6.6.5. In regard to the impact on PICs, it has been concluded that the proposed scheme will not exacerbate

any existing patterns of PICs occurring on the surrounding highway network.

6.6.6. This Chapter of the TA has also set out that the NWRR will provide a number of wider benefits to

Northampton, summarised as follows:

The scheme will reduce traffic flows on a number of significant links and junctions in Northampton

when compared to the Do Minimum case;

The scheme has a strong business case with a high Benefit/Cost Ratio (BCR) which demonstrates

that the savings, predominantly to travel time, outweigh the cost of delivering the scheme by 7

times, a very high return for a transport scheme;

The scheme provides additional capacity on the transport network to support housing growth

targets; and

The scheme will provide additional resilience to the Northampton highway network when disruption

arises from time to time, such as planned roadworks, accidents or other foreseen and unforeseen

events.


7 IMPACT ON INDIVIDUAL JUNCTIONS

7.1 INTRODUCTION

7.1.1. From the Traffic Impact Assessment detailed in Chapter 6, a number of junctions have been taken

forward for individual junction capacity assessments. These junctions were informed by the analysis

of the NSTM results which showed that the proposed scheme would have a significant impact. The

scope of the capacity assessments has been agreed with NH’s Development Control Team.

7.1.2. This Chapter assesses the impacts of the NWRR on individual junctions on the surrounding highway

network. Following this, Chapter 8 sets out the mitigation proposals deemed necessary as a result of

the impact of the proposed scheme and Chapter 9 re-evaluates those impacts and sets out the

Monitor and Manage Strategy proposed.

7.1.3. The following eight junctions have been taken forward for individual junction capacity assessments,

with their locations illustrated in Figure 7-1 (overleaf):

J1: A508 Harborough Road / Pitsford High Street Priority Junction;

J2: A508 Harborough Road / Brampton Lane Priority Junction;

J3: A508 Harborough Road / Brampton Lane / Vyse Road Roundabout;

J4: A508 Harborough Road / A5076 Holly Lodge Drive Signalised Junction;

J5: A5199 Northampton Road / Brampton Lane / Welford Road Priority Junction (existing and

proposed);

J6: A5199 Northampton Road / Sandy Lane Priority Junction (existing and proposed);

J7: A428 Harlestone Road / New Sandy Lane / York Way Roundabout; and

J8: New Sandy Lane / Berrywood Road / Roman Road Double Mini Roundabout.


Figure 7-1 - Assessed Junction Locations

7.2 MODELLING APPROACH

7.2.1. The strategic traffic modelling analysis presented in section 6.3 identified that the above junctions

would become congested as a result of the proposed scheme. These junctions are located on routes

where there is a forecast increase in traffic flows and high junction volume / capacity ratio as shown

in Table 6-2.

7.2.2. Modelled traffic flows for the scenarios detailed in paragraph 6.2.3 have been extracted from the

NSTM and used in the individual junction models. These traffic flows utilised for the individual junction

model are the demand flows which suggest that a more robust case has been considered in analysing

the junction capacity assessment. However, as noted in paragraph 6.2.10 above, localised adjustment

factors have been applied to a number of junctions to account for the differences in the base year

modelled and observed flows. In order to account for these differences, 2015 proportions (turning

count percentages) have been applied to the NSTM modelled flows for a number of junctions which

were not calibrated against the 2015 observed flows. Applying these proportions to the NSTM

modelled flows provides a more realistic interpretation of the traffic movements at the following

individual junctions:

J1: A508 Harborough Road / Pitsford High Street Priority Junction

J3: A508 Harborough Road / Brampton Lane / Vyse Road Roundabout

J5: A5199 Northampton Road / Brampton Lane / Welford Road Priority Junction


J5: A5199 Northampton Road / Brampton Lane / Welford Road Proposed Roundabout

J7: A428 Harlestone Road / New Sandy Lane / York Way Roundabout

7.2.3. The following industry standard software programs have been used to individually model the different

junction types and layouts:

PICADY, which is part of the Junctions 9 software, has been used to model priority junctions;

ARCADY, which is also part of the Junctions 9 software, has been used to model roundabout

junctions; and

LINSIG, has been used to model signalised junctions.

7.2.4. The outputs from the above software programs provide information about a junction’s operation via a

number of key parameters which indicate a junction’s operational performance. The key measures for

each software program have been highlighted and described in more detail below.

Junctions 9 (ARCADY and PICADY)

7.2.5. The main measures of junction performance in ARCADY and PICADY are:

Ratio of Flow to Capacity (RFC);

Maximum Queue Length; and

Delay in seconds per vehicle.

7.2.6. The main indication of a junction’s performance is provided by the RFC for each arm. The industry

agreed ideal RFC maximum is 0.85 (equivalent to 85%), as when junctions approach and exceed this

value, traffic queues and delays increase exponentially.

LINSIG

7.2.7. The main measures of junction performance in LINSIG are:

Practical Reserve Capacity (PRC)

Degree of Saturation (DoS); and

Mean Maximum Queue (MMQ).

7.2.8. The main indication of a junction’s performance is provided by the junction’s PRC. In traffic

engineering, the PRC of a traffic signal junction is a commonly used measure of its available spare

capacity. The practical reserve capacity is related to the degree of saturation of a traffic signal junction.

A positive PRC indicates that a junction has spare capacity and may be able to accept more traffic. A

negative PRC indicates that the junction is over capacity and is suffering from traffic congestion. A

junction where the degree of saturation exceeds a threshold of 90% on most movements is likely to

have a negative PRC and therefore would be operating above its practical capacity.

7.3 JUNCTION CAPACITY ASSESSMENTS

7.3.1. The results of the individual junction capacity assessments undertaken for the existing and proposed

layouts are provided in the following sub-sections.

J1: A508 Harborough Road / Pitsford High Street Priority Junction

7.3.2. The existing Harborough Road / Pitsford High Street priority junction has been modelled using

Junctions 9 software for all scenarios listed in paragraph 6.2.3. As noted above in paragraph 7.2.1,


the traffic flows used in this junction model have been proportioned by the 2015 observed flows to

provide a more robust assessment.

7.3.3. The results are presented in Table 7-1 below, with the full output report provided in Appendix H.

Table 7-1: A508 Harborough Road / Pitsford High Street Existing Priority Junction

AM PM

Queue (PCU)

Delay (s/PCU)

RFC Queue (PCU)

Delay (s/PCU)

RFC

2015 Base

High Street (left turn onto Harborough Road S)

0.3 11.06 0.20 0.2 9.60 0.16

High Street (right turn onto Harborough Road N)

0.6 26.12 0.37 0.4 23.70 0.31

Harborough Road S (straight on / right turn onto High Street)

2.5 9.01 0.55 2.1 5.91 0.47

2021 DM


0.4 16.27 0.3 0.2 11.15 0.19


1.2 50.48 0.57 0.7 36.7 0.41


5.9 15.47 0.74 4.8 8.95 0.66

2021 DS


0.3 14.11 0.23 1.7 54.1 0.67


0.9 46.45 0.49 3.4 119.37 0.83


6.1 16.33 0.75 7.3 12.5 0.76

2031 DM


0.3 14.31 0.21 0.1 10.84 0.12


1.3 76.5 0.59 0.7 61.64 0.42


13.5 36.07 0.89 42.4 95.38 1.01

2031 DS


0.2 14.35 0.19 5.1 179.72 1.09


0.8 51.52 0.46 4.7 218.43 1.01


5.4 15.89 0.72 70.9 154.08 1.07


7.3.4. The results in Table 7-1 indicate that the junction operates within capacity in the 2015 base year and

the 2021 future year scenarios during both peak hours.

7.3.5. The junction starts to operate over capacity in the 2031 Do Minimum scenario with an RFC of 0.89 in

the AM peak hour and 1.01 in the PM peak hour on Harborough Road South. This is likely due to

queueing as there is no stacking capacity for vehicles to turn right, therefore one PCU can block the

junction, resulting in queues on the major arm. The junction operates over-capacity for all movements

in the Do Something scenario where RFC values range from 1.01-1.09 in the PM peak hour.

7.3.6. Although the junction performs worse in the Do Something scenario when the proposed scheme is

introduced, no mitigation is proposed at this current time. Instead, this junction will be included as part

of the Monitor and Manage Strategy, and the reasons why this junction has been chosen for this

Strategy is explained in Chapter 9 of this report.

J2: A508 Harborough Road / Brampton Lane Priority Junction

7.3.7. The existing Harborough Road / Brampton Lane priority junction south of the A508 Harborough Road

/ Pitsford High Street junction has been modelled in the Junctions 9 software for all the scenarios

listed in paragraph 6.2.3. The results are presented in Table 7-2 below, with the full output report

provided in Appendix H.

Table 7-2 - A508 Harborough Road / Brampton Lane Existing Priority Junction

AM PM

Queue (PCU)

Delay (s/PCU)

RFC Queue (PCU)

Delay (s/PCU)

RFC

2015 Base

Brampton Lane (left turn onto Harborough Road N)

0.8 11.77 0.44 1.1 15.28 0.52

Brampton Lane (right turn onto Harborough Road S)

0.0 0.00 0.00 0.0 0.00 0.00

Harborough Road N (straight on / right turn onto Brampton Lane)

4.8 15.02 0.73 4.0 14.42 0.71

2021 DM


1.5 16.94 0.60 2.3 25.48 0.71


0.0 0.00 0.00 0.0 0.00 0.00


26.2 79.55 0.98 36.4 132.60 1.04

2021 DS


0.2 8.75 0.14 0.2 11.02 0.17


0.0 0.00 0.00 0.0 0.00 0.00


3.1 7.13 0.54 2.3 5.76 0.44


AM PM

Queue (PCU)

Delay (s/PCU)

RFC Queue (PCU)

Delay (s/PCU)

RFC

2031 DM


1.9 20.84 0.66 31.4 285.61 1.30


0.2 63.24 0.16 4.2 526.88 1.11


98.8 326.34 1.17 74.8 276.39 1.16

2031 DS


0.5 10.79 0.32 27.7 295.56 1.42


0.2 54.12 0.15 3.2 561.62 1.20


107.7 314.81 1.17 70.1 229.60 1.13

7.3.8. The results in Table 7-2 above indicate that the existing priority junction operates within capacity in

the 2015 base year scenario during both peak hours. The junction becomes over-capacity in the 2021

Do Minimum scenario with the A508 Harborough Road North experiencing RFC values of 0.98 and

1.05. This is likely to be caused by vehicles waiting to turn right onto Brampton Lane as there is no

stacking capacity for vehicles to turn right, therefore one PCU can block the junction, resulting in

queues on the major arm.

7.3.9. The junction operates within capacity in the 2021 Do Something scenario, due to a reduced amount

of traffic forecast to right from Harborough Road North to Brampton Lane and traffic turning left from

Brampton Lane to Harborough Road North with the scheme built, thereby enabling increased

throughput of traffic along the major arm.

7.3.10. In both the 2031 Do Minimum and Do Something scenarios, the junction is expected to operate over-

capacity. Brampton Lane experiences capacity issues in the 2031 Do Minimum scenario, with an RFC

of 1.30 in the PM peak hour. The A508 Harborough Lane North continues to operate over-capacity in

both the peak hours, with RFC’s of 1.17 and 1.16 in the AM and PM peak hours, respectively.

7.3.11. The results show the junction operates the worse in the PM peak hour of the Do Something scenario,

with RFC values ranging from 1.13-1.42 on all movements. Although the queues are low, and delays

are only slightly higher than the Do Minimum scenario.

7.3.12. Although the junction performs worse in the Do Something scenario when the proposed scheme is

introduced, no mitigation is proposed at this current time. Instead, this junction will be included as part

of the Monitor and Manage Strategy, and the reasons why this junction has been chosen for this


J3: A508 Harborough Road / Brampton Lane / Vyse Road Existing Roundabout

7.3.13. The existing A508 Harborough Road / Brampton Lane / Vyse Road roundabout in Boughton, has been

modelled in the Junctions 9 software for all the scenarios listed in paragraph 6.2.3. As noted in


paragraph 7.2.1, the traffic flows used in this junction model have been proportioned by the 2015

observed flows to provide a more robust assessment.


Table 7-3: A508 Harborough Road / Brampton Lane / Vyse Road Existing Roundabout

AM PM

Queue (PCU)

Delay (s/PCU)

RFC Queue (PCU)

Delay (s/PCU)

RFC

2015 Base

Arm A – Vyse Road (E) 0.6 7.61 0.37 1.3 9.88 0.57

Arm B – A508 Harborough Road (S) 0.6 3.15 0.35 1.1 4.34 0.52

Arm C – Brampton Lane (W) 1.5 9.72 0.60 0.8 8.20 0.44

Arm D - A508 Harborough Road (N) 0.8 4.47 0.44 0.5 3.21 0.33

2021 DM

Arm A – Vyse Road (E) 0.9 9.75 0.47 2.3 14.85 0.71




2021 DS

Arm A – Vyse Road (E) 15.7 110.46 1.00 172.1 997.14 1.53




2031 DM

Arm A – Vyse Road (E) 3.9 28.65 0.81 49.9 190.36 1.11




2031 DS

Arm A – Vyse Road (E) 76.9 422.27 1.26 234.7 1138.71 1.53




7.3.15. The results in Table 7-3 above indicate that the junction is operating within capacity in the 2015 base

year and the 2021 Do Minimum scenario in both peak hours.


7.3.16. The junction starts to operate over-capacity in the 2021 Do Something scenario in both peak hours

as Vyse Road (E) and Brampton Lane (W) experience RFC values over 1.00. The junction continues

to operate over-capacity in the 2031 Do Minimum scenario when the proposed scheme is built, albeit

RFC values on both Vyse Road (E) and Brampton Lane (W) are slightly lower when compared to the

2021 Do Something scenario.

7.3.17. In the 2031 Do Something scenario, the junction continues to operate over-capacity, with RFC values

recorded at 1.26 and 1.53 at Vyse Road (E) and 1.86 and 1.74 at Brampton Lane (W) during the

respective AM and PM peak hours. Significant delays are also expected, with 19 minute delays in the

PM peak hour on Vyse Road (E) and 38 minute delays in the AM peak hour on Brampton Lane (W).

7.3.18. In summary, the A508 Harborough Road / Brampton Lane / Vyse Road Roundabout operates within

capacity in the 2015 Base Year and 2021 Do Minimum scenarios. The roundabout is forecast to

operate over capacity and experience congestion and delays in the 2021 Do Something and both

2031 future year scenarios.

7.3.19. As the junction operates over-capacity in both 2031 future year scenarios, mitigation measures have

been designed and will be implemented at this location as part of the NWRR proposals. The mitigated

design is detailed and assessed in section 8.4 of this report

J4: A508 Harborough Road / A5076 Holly Lodge Drive Existing Signalised Junction

7.3.20. The existing layout of the A508 Harborough Road / A5076 signalised junction has been modelled in

LinSig for all scenarios listed in paragraph 6.2.3. The junction operates on a single controller and

stage stream with both traffic and pedestrian phases using MOVA. The model has been run with a

cycle time of 120 seconds for each scenario.


Table 7-4: A508 Harborough Road / A5076 Holly Lodge Existing Signalised Junction

Arm Lane Description

AM PM

DoS (%) Mean Max

Queue (PCU) DoS

Mean Max Queue (PCU)

2015 Base

1/2+1/1. Holly Lodge Drive Left Right

63.9% 10.6 84.1% 22.2

2/1+2/2 Harborough Road S Right + Ahead

47.3% 7.5 85.5% 22.9

3/2+3/1 Harborough Road N Left + Ahead

64.4% 8.6 63.8% 8.6

PRC (Over All Lanes) 39.4% 5.3%

2021 DM


73.1% 13.7 87.2% 23.3


50.6% 8.8 87.6% 25.0



AM PM

DoS (%) Mean Max

Queue (PCU) DoS



74.4% 11.1 67.0% 9.2


2021 DS


71.2% 14.4 80.8% 20.2


52.4% 8.7 80.9% 20.1


71.2% 9.6 64.9% 8.4


2031 DM


85.5% 19.0 101.3% 40.3


49.7% 8.9 100.5% 49.6


85.1% 14.0 79.2% 12.2

PRC (Over All Lanes) 5.3% -12.5%

2031 DS


73.8% 17.1 86.1% 22.0


47.9% 7.0 86.2% 23.6


74.8% 12.3 68.4% 11.2


7.3.22. The modelling results shown in Table 7-4 above indicate that the junction operates over capacity in

the 2031 Do Minimum scenario in the PM peak, however it will operate well within capacity in all the

future year Do Something scenarios. This is due to reassignment of the traffic flows due to the NWRR

and showing benefit at this junction. Accordingly, it is concluded that the proposed scheme will have

a positive traffic impact at this junction.

7.3.23. Despite the above, NH requested that this junction be improved as traffic is likely to access the NWRR

at this location rather than routing through the villages of Boughton and Moulton, where traffic calming

is proposed in support of this TA. As a result, mitigation measures will be implemented at this junction

as part of the NWRR proposals. The mitigated design is detailed and assessed in Section 8.6 of this

report.


J5: A5199 Northampton Road / Brampton Lane / Welford Road Existing Priority Junction

7.3.24. As detailed in Section 5.3, the A5199 Northampton Road / Brampton Lane / Welford Road existing

priority junction will be converted into a four-arm roundabout junction as part of the proposed scheme.

Therefore, the existing A5199 Northampton Road / Brampton Lane / Welford Road Priority Junction

has been modelled in the Junctions 9 software for just the 2015 Base, 2021 and 2031 Do Minimum

scenarios where the proposed scheme does not get built.

7.3.25. As noted in paragraph 7.2.1, the traffic flows used in this junction model have been proportioned by

the 2015 observed flows to provide a more robust assessment. The results are presented in Table 7-

5 below, with the full output report provided in Appendix H.

Table 7-5: A5199 Northampton Road / Brampton Lane / Welford Road Existing Priority

Junction

AM PM

Queue (PCU)

Delay (s/PCU)

RFC Queue (PCU)

Delay (s/PCU)

RFC

2015 Base

Arm A - Northampton Road (left turn onto Brampton Lane)

0.5 11.49 0.33 0.20 9.59 0.16

Arm B - Brampton Lane (right turn onto Northampton Road)

3.0 48.4 0.76 15.5 167.62 1.03

Arm C - Welford Road (straight on / Right turn onto Brampton Lane)

0.9 7.28 0.32 0.60 6.18 0.25

2021 DM


0.7 13.9 0.41 0.20 10.04 0.18


6.4 89.4 0.9 36.5 349.57 1.2


0.8 7.26 0.31 0.80 6.36 0.28

2031 DM


1.5 22.3 0.61 0.3 11.73 0.25


75.8 849.59 1.51 141.3 1461.52 1.76


1.8 9.04 0.48 1.1 7.12 0.35

7.3.26. Table 7-5 show all arms but one approach is operating within capacity in the 2015 base year scenario.

This exception is at Brampton Lane with an RFC value of 1.03 in the PM peak hour. Similarly, in the

2021 Do Minimum scenario, Brampton Lane operates at capacity in the AM peak with an RFC value

of 0.9 and over capacity in the PM peak hour with an RFC value of 1.2.


7.3.27. In the 2031 Do Minimum scenario, Brampton Lane is forecast to operate over capacity with an RFC

value of 1.51 in the AM peak hour and 1.76 in the PM peak hour, resulting in significant delays of 14

and 24 minutes in the AM and PM hours, respectively.

J5: A5199 Northampton Road / Brampton Lane / Welford Road Proposed Roundabout

7.3.28. As part of the NWRR proposals, the existing layout of the A5199 Northampton Road / Brampton Lane

/ Welford Road Priority Junction will be reconfigured into a four-arm roundabout. The proposals include

the realignment of the existing A5199 Northampton Road with Brampton Road as described in Section

5.3 and shown in Figure 5-4 above.

7.3.29. The proposed A5199 Northampton Road / Brampton Lane / Welford Road Roundabout has been

modelled in the Junctions 9 software for the 2021 and 2031 Do Something scenarios.

7.3.30. The proposed roundabout has been modelled with a flat traffic profile for each movement, rather than

a synthesised peak (as per the existing priority junction). This is appropriate in this case, given that

the network is likely to experience increased congestion in 2021 and 2031, thereby flattening traffic

profiles across the network. Additionally, as noted in paragraph 7.2.1, the traffic flows used in this

junction model have been proportioned by the 2015 observed flows to provide a more robust

assessment.


Table 7-6 - A5199 Northampton Road / Brampton Lane / Welford Road Proposed Roundabout

AM PM

Queue (PCU)

Delay (s/PCU)

RFC Queue (PCU)

Delay (s/PCU)

RFC

2021 DS

Arm A - A5199 Northampton Road (W)

6.3 14.39 0.87 6.3 14.30 0.87

Arm B – Boughton Farm (N) 0.0 0.00 0.00 0.0 0.00 0.00

Arm C - Brampton Lane (E) 2.2 7.52 0.69 3.0 9.35 0.75

Arm D - A5199 Welford Road (S) 1.1 5.72 0.50 1.8 8.76 0.64

2031 DS

Arm A - A5199 Northampton Road (W)

6.4 14.53 0.87 6.9 15.17 0.88

Arm B – Boughton Farm (N) 0.0 0.00 0.00 0.0 0.00 0.00

Arm C - Brampton Lane (E) 4.0 11.46 0.80 3.5 10.70 0.78

Arm D - A5199 Welford Road (S) 1.1 6.11 0.51 1.1 6.62 0.51

7.3.32. As shown in Table 7-6, the proposed roundabout is expected to operate broadly within capacity in

both the 2021 and 2031 Do Something scenarios, when the proposed scheme is built. The A5199

Northampton Road (W) experiences an RFC of 0.87 and 0.88 in the AM and PM peak hours,

respectively, with minimal queueing and delay. As such, it can be concluded that the proposed layout

is therefore appropriate for future year operation.


J6: A5199 Northampton Road / Sandy Lane Existing Priority Junction

7.3.33. As detailed in Section 5.3, the A5199 Northampton Road / Sandy Lane existing priority junction will

be converted into a four-arm roundabout junction as part of the proposed scheme. Therefore, the

existing priority junction has been modelled in Junctions 9 only for the 2015 Base, 2021 and 2031 Do

Minimum scenarios where the proposed scheme isn’t built.


Table 7-7 - A5199 Northampton Road / Sandy Lane Existing Priority Junction

AM PM

Queue (PCU)

Delay (s/PCU)

RFC Queue (PCU)

Delay (s/PCU)

RFC

2015 Base

Arm A - A5199 Northampton Road E (right turn onto Sandy Lane)

0.0 0.0 0.0 0.0 0.0 0.0

Arm B - Sandy Lane (left onto A5199 Northampton Road E)

2.0 26.90 0.67 12.8 120.05 0.99

Arm C - A5199 Northampton Road W (straight on/ left turn onto Sandy Lane)

0.0 0.0 0.0 0.0 0.0 0.0

2021 DM


0.00 0.00 0.00 0.00 0.00 0.00


2.6 34.19 0.74 28.7 232.99 1.11


0.00 0.00 0.00 0.00 0.00 0.00

2031 DM


0.00 0.00 0.00 0.00 0.00 0.00


62.7 549.39 1.31 53.6 467.96 1.28


0.00 0.00 0.00 0.00 0.00 0.00

7.3.35. The results in Table 7-7 above indicate that the junction currently operates at-capacity during the PM

peak hour in the 2015 base year scenario. Sandy Lane (for vehicles turning right onto Northampton

Road) experiences an RFC of 0.99 in the PM peak hour. This is likely a result of vehicles being unable

to find sufficient gaps to turn on to the main arm of the junction (A5199 Northampton Road) due to

high volumes of through traffic, thereby causing queuing (up to 13 PCUs) on Sandy Lane as vehicles

are unable to exit the junction.

7.3.36. The capacity issues are exacerbated in the 2021 and 2031 Do Minimum scenarios. Sandy Lane

becomes significantly over-capacity for both left and right turn movements, with the maximum RFC


reaching 1.31 in the AM peak hour and 1.28 in the PM peak hour. Again, this is likely due to a high

volume of through traffic along A5199 Northampton Road, causing queuing on Sandy Lane.

J6: A5199 Northampton Road / Sandy Lane / NWRR Proposed Roundabout

7.3.37. The A5199 Northampton Road / Sandy Lane / NWRR four arm Roundabout is a new proposed layout

that will provide the northern connection of the NWRR to the existing road network. The proposed

layout will convert the existing A5199 Northampton Road / Sandy Lane Junction into a four-arm

roundabout with the southern arm providing the NWRR link. The proposals are described in more

detail in Section 5.3 and shown in Figure 5-3 above.

7.3.38. The proposed A5199 Northampton Road / Sandy Lane / NWRR Roundabout has been modelled in

Junctions 9 for the 2021 Do Something and 2031 Do Something scenarios. Similarly, to the proposed

A5199 Northampton Road / Brampton Lane / Welford Road Roundabout, the A5199 Northampton

Road / Sandy Lane / NWRR proposed roundabout junction has been modelled with a flat traffic profile

for each movement, rather than a synthesised peak (as per the existing priority junction). This is

appropriate in this case, given that the network is likely to experience increased congestion in 2021

and 2031, thereby flattening traffic profiles across the network.


Table 7-8 - A5199 Northampton Road / Sandy Lane / NWRR Proposed Roundabout

AM PM

Queue (PCU)

Delay (s/PCU)

RFC Queue (PCU)

Delay (s/PCU)

RFC

2021 DS

Arm A – Sandy Lane (W) 0.1 3.67 0.09 0.3 5.10 0.23

Arm B – A5199 Welford Road (N) 0.6 4.11 0.37 0.3 3.69 0.23

Arm C - A5199 Welford Road (E) 2.3 5.59 0.69 3.6 8.05 0.77

Arm D - NWRR (S) 1.0 3.85 0.49 1.2 4.49 0.55

2031 DS

Arm A – Sandy Lane (W) 0.2 5.07 0.14 0.6 7.07 0.34

Arm B – A5199 Welford Road (N) 0.7 4.94 0.42 0.5 4.60 0.30

Arm C - A5199 Welford Road (E) 6.1 12.67 0.86 4.4 9.43 0.82

Arm D - NWRR (S) 3.4 9.14 0.78 3.7 9.22 0.79

7.3.40. The results shown in Table 7-8 indicate that the proposed junction is expected to operate within

capacity in the 2021 Do Something scenario for both peak hours. The proposed junction is forecast

to operate broadly within capacity in the 2031 Do Something scenario in the AM peak hour, with an

RFC of 0.86 experienced on the A5199 Welford Road (E) with minimal queueing and delays. As such,

it can therefore be concluded that the proposed layout is appropriate for future year operation.

J7: A428 Harlestone Road / New Sandy Lane / York Road Existing Roundabout

7.3.41. The A428 Harlestone Road / New Sandy Lane / York Road Roundabout has been modelled in the

Junctions 9 software for all the scenarios listed in paragraph 6.2.3. The roundabout will provide the


Southern connection of the NWRR to the existing road network with the NWRR joining the York Way

(W) arm of the junction.

7.3.42. As noted in paragraph 7.2.1, the traffic flows used in this junction model have been proportioned by

the 2015 observed flows to provide a more robust assessment.

7.3.43. The modelling results are presented in Table 7-9 below, with the full Junctions 9 output report provided

in Appendix H.

Table 7-9 - A428 Harlestone Road / New Sandy Lane / York Road Existing Roundabout

AM PM

Queue (PCU)

Delay (s/PCU)

RFC Queue (PCU)

Delay (s/PCU)

RFC

2015 Base

Arm A – York Way (E) 0.0 0.00 0.00 0.0 0.00 0.00

Arm B – A428 Harlestone Road (S) 1.7 6.45 0.63 1.1 5.44 0.53

Arm C – New Sandy Lane (W) 0.9 4.64 0.46 0.5 3.5 0.32

Arm D - A428 Harlestone Road (N) 0.4 2.94 0.25 0.8 3.82 0.43

2021 DM

Arm A – York Way (E) 0.0 2.42 0.04 0.0 2.85 0.03




2021 DS

Arm A – York Way (E) 2.2 6.89 0.69 3.5 10.85 0.78




2031 DM

Arm A – York Way (E) 0.0 2.74 0.05 0.0 3.13 0.04




2031 DS

Arm A – York Way (E) 3.2 9.73 0.77 5.3 15.23 0.85




7.3.44. As shown in Table 7-9, the roundabout is currently operating within capacity in the 2015 base year,

and will continue to do in both 2021 future year scenarios.


7.3.45. In the 2031 Do Minimum 2031 scenario, the results indicate that the roundabout will operate over-

capacity on Harlestone Road South, with an RFC value of 0.93 and 0.87 in the AM and PM peak

hours, respectively. The situation is exacerbated in the 2031 Do Something scenario as both

Harlestone Road South and New Sandy Lane operate significantly over-capacity, with RFC’s of above

1.0 and delays of over 4 minutes in the AM peak hour.

7.3.46. In summary, the modelling results indicate that the A428 Harlestone Road / New Sandy Lane / York

Road Roundabout operates within capacity in the 2015 base year and will continue to operate within

capacity in both 2021 future year scenarios. However, it is forecast that the roundabout will operate

over capacity in both 2031 future year scenarios.

7.3.47. As the junction operates over-capacity in both 2031 future year scenarios, mitigation measures have

been designed and will be implemented at this location as part of the NWRR proposals. The mitigated

design is detailed and assessed in section 8.5 of this report.

J8: Roman Road / New Sandy Lane / Berrywood Road / Sandy Lane Proposed Roundabout

7.3.48. As part of the Norwood Farm development proposals (which propose a residential-led mixed use

sustainable urban extension on land south of Roman Road), the existing junction (double mini-

roundabout) will be reconfigured into a single four-arm single roundabout which will connect to the

Sandy Lane Relief Road and the Norwood Farm proposed development site . This change in junction

layout is scheduled to happen whether or not the proposed scheme is built and therefore an

assessment of the existing junction has not been undertaken.

7.3.49. In agreement with NH and NCC, the reconfiguration of the existing Double Mini-Roundabout into a

single four arm roundabout has been included as a committed highway infrastructure scheme in both

the 2021 and 2031 future year modelling scenarios in the NSTM. Therefore, the proposed roundabout

has been modelled in Junctions 9 for all the 2021 and 2031 future year scenarios. The modelling

results are presented in Table 7-10 below, with the full Junctions 9 output report provided in Appendix

H.

7.3.50. The proposed junction layout prepared by Peter Brett Associated (PBA) is shown on Drawing

32486/2501/SK08 Rev D, provided in Appendix I.

Table 7-10 - Roman Road / New Sandy Lane / Berrywood Road / Sandy Lane Proposed

Roundabout

AM PM

Queue (PCU)

Delay (s/PCU)

RFC Queue (PCU)

Delay (s/PCU)

RFC

2021 DM

Arm A – Berrywood Road (E) 1.6 9.34 0.62 0.6 5.22 0.37

Arm B – Sandy Lane (S) 1.5 6.12 0.59 2.6 8.79 0.71

Arm C – Roman Road (W) 0.9 6.42 0.46 0.5 5.52 0.31

Arm D - New Sandy Lane (N) 1.1 4.79 0.51 1.2 4.95 0.53

2021 DS



AM PM

Queue (PCU)

Delay (s/PCU)

RFC Queue (PCU)

Delay (s/PCU)

RFC

Arm B – Sandy Lane (S) 1.7 6.80 0.62 4.5 13.72 0.82

Arm C – Roman Road (W) 1.0 7.26 0.50 0.5 6.43 0.34


2031 DM


Arm B – Sandy Lane (S) 5.1 16.39 0.84 30.5 76.00 1.01

Arm C – Roman Road (W) 3.9 20.89 0.80 1.8 13.20 0.65


2031 DS


Arm B – Sandy Lane (S) 10.1 29.69 0.92 95.6 200.00 1.13

Arm C – Roman Road (W) 9.9 51.90 0.94 2.2 15.79 0.69


7.3.51. The modelling results in Table 7-10 above indicate that the proposed roundabout will operate well

within capacity during the 2021 Do Something and Do Minimum future year scenarios in both peak

hours.

7.3.52. However, the junction is expected to operate significantly over capacity in both 2031 future year

scenarios. Both Berrywood Road and Sandy Lane are predicted to exceed theoretical capacity with

RFC values above 1.00 in the 2031 Do Minimum scenario in either the AM or PM peak hours. In the

2031 Do Something scenario, all arms are recorded to exceed theoretical capacity in the AM peak,

with RFC values ranging from 0.89 – 1.05 in the AM peak. In the PM peak hour, New Sandy Lane

also exceeds practical capacity with an RFC value of 0.88, whereas Sandy Lane exceeds theoretical

capacity with an RFC value of 1.13, experiencing significant delays and queuing.

7.3.53. Although the junction performs worse in the 2031 Do Something scenario when the proposed scheme

is introduced, no mitigation is proposed at this current time. Instead, this junction will be included as

part of the Monitor and Manage Strategy, and the reasons why this junction has been chosen for this


7.4 SUMMARY

7.4.1. The results of the junction capacity assessments indicate that the proposed scheme is likely to have

an adverse effect on a number of individual off-site junctions along the surrounding highway network.

As a result, high-level mitigation measures have been designed at the following junctions. These are

detailed and assessed in Chapter 8 of this report. The mitigation schemes are designed for:

J3: A508 Harborough Road / Brampton Lane / Vyse Road Roundabout; and

J7: A428 Harlestone Road / New Sandy Lane / York Way Roundabout.

7.4.2. In addition to the above, a number of other junctions have also been identified as being adversely

impacted by the proposed scheme, although mitigation measures are not proposed at this current


time. Instead, a Monitor and Manage Strategy has been proposed at the following junctions which are

discussed in Chapter 9 of this report.


J2: A508 Harborough Road / Brampton Lane Priority Junction; and

J8: New Sandy Lane / Berrywood Road / Roman Road / Sandy Lane Proposed Roundabout.

7.4.3. The junction capacity assessments also revealed that the proposed access junctions are expected to

operate within theoretical capacity in both the 2021 and 2031 Do Something future year scenarios

and are therefore appropriate for future year operation.


8 MITIGATION MEASURES

8.1 INTRODUCTION

8.1.1. This section puts forward the proposed measures, deemed necessary, that will mitigate the impacts

of the proposed scheme following the Traffic Impact Assessment contained within Chapter 6 and the

junction capacity assessments contained within Chapter 7. This section also details the mitigation

measures provided following further analysis of the modelling results, as well as scoping discussions

with NH’s Development Control Team.

8.1.2. In addition to the mitigation measures identified in this Chapter, a Monitor and Manage Strategy is

proposed at some junctions detailed in Chapter 9 of this report.

8.1.3. It should be noted that all mitigation schemes will be subject to the road safety audit process in

accordance with the DMRB GG 11910.

8.2 MITIGATION SCHEMES (OVERVIEW)

8.2.1. Comparisons of the modelling results for the Do Minimum and the Do Something scenarios and

discussions with officers from NH’s Development Control team highlighted that the following would be

likely to occur which are attributable to the proposed scheme:

Increased volume of vehicle traffic routing through the villages of Moulton and Boughton;

Vehicles would experience significant congestion and delay at A508 Harborough Road / Brampton

Lane / Vyse Road Existing Roundabout, particularly on the Vyse Road and Brampton Lane arms

of the junction (J3); and

Vehicles would experience significant congestion and delay at the A428 Harlestone Road / New

Sandy Lane / York Road Roundabout, particularly on the A428 Harlestone Road and New Sandy

Lane (J7).

8.2.2. In addition to the above, following the submission of the original TA (May 2019), NH requested that

the TAA provided details of a mitigation scheme at the A508 Harborough Road / A5076 Holly Lodge

Drive signalised junction (J4). The reasoning for this is that traffic is likely to access the NWRR via the

A508 Harborough Road / A5076 Holly Lodge Drive junction, rather than routing through the villages

of Boughton and Moulton, given the strategic nature of the A508 and A5076 and the fact that measures

are proposed to make the routes through Boughton and Moulton less attractive.

8.2.3. Following the submission of the TAA in September 2019, traffic calming measures are still proposed

in the villages of Moulton and Boughton (see paragraph 8.3.4 below) and therefore a mitigation

scheme is provided at the A508 Harborough Road / A5076 Holly Lodge Drive signalised junction to

encourage users to travel through this junction, rather than rat-running through the villages.

10 Design Manual for Roads and Bridges: General Principles and Scheme Governance (GG 119) Road Safety Audit


8.2.4. Based on the latest NSTM model runs and the individual junction modelling assessment undertaken

in this TA, the measures identified in the original TA (May 2019) and TAA (September2019) are still

appropriate.

8.2.5. In light of the above, the following mitigation measures will be implemented as part of the NWRR

proposals:


Mitigation Scheme 2: Capacity Improvements at A508 Harborough Road / Brampton Lane / Vyse

Road Roundabout (J3);

Mitigation Scheme 3: Capacity Improvements at A428 Harlestone Road / New Sandy Lane / York

Road Roundabout (J7); and

Mitigation Scheme 4: Capacity improvements at the A508 Harborough Road / A5076 Holly Lodge

Drive Signalised Junction (J4).

8.2.6. The mitigation schemes identified above are detailed and assessed in the following sub-sections of

this report.

8.3 MITIGATION SCHEME 1

8.3.1. During pre-application scoping discussions with NH (refer to Appendix J) in support of the TA dated

May 2019, it was understood that although the proposed scheme would result in a significant uplift in

vehicle trips within the villages of Boughton and Moulton, mitigation targeted at individual junctions

along these routes would only provide extra capacity, therefore encouraging their usage and potential

rat-running. Instead, it was agreed that any mitigation proposed would need to discourage vehicles

from routing through Boughton and Moulton in order to reduce the traffic forecasted to route through

these villages.

8.3.2. Following the submission of the original TA (May 2019) and subsequent TAA (September 2019), the

Do Minimum and Do Something traffic flows in Boughton and Moulton have been reviewed to

understand whether the updated NSTM forecasts a significant uplift in traffic in such areas. The results

confirm that traffic flows have been reassigned when the proposed scheme is introduced which would

lead to an increase in traffic in some areas. As a result, it has been determined that mitigation should

still be proposed in the form of traffic calming measures. The SATURN plots which show this uplift in

trips are contained within Appendix J.

8.3.3. Liaison has been undertaken with members of NH’s Road Safety Team and Highways Engineering

Team. The purpose of this has been to understand better the likely impacts of the different potential

traffic calming measures and to understand better the deliverability, feasibility and acceptability of

various measures in the context of the local area. The liaison has led to the following refined selection

of traffic calming measures being proposed as part of the scheme:

Traffic Calming Scheme A: The introduction of a “Give way to oncoming vehicles” pinch point

feature on the section of Vyse Road between Harborough Road and Howard Lane; and

Traffic Calming Scheme B: Enhancing the “Give way to oncoming vehicles” pinch point feature

located outside the entrance of Boughton Primary School.

8.3.4. The above traffic calming measures have been proposed to make the villages less attractive as a

through route. Therefore, to complement the above, capacity improvements will also be provided at

the A508 Harborough Road / A5076 Holly Lodge Drive Signalised Junction (see description provided


in paragraph 8.6.2 below for further details). This is because the junction forms part of the strategic

route that any vehicles discouraged from travelling through the villages may use as an alternative to

access the NWRR.

8.3.5. The primary aim of Mitigation Scheme 1 is to encourage drivers who do not have an origin or

destination in or around Moulton and Boughton to use more appropriate routes to access and egress

the NWRR rather than routing through the villages. The traffic calming measures outlined above will

create new, or enhance existing, pinch-points for vehicles travelling through Boughton and Moulton,

lengthening the journey times which will therefore result in a less attractive route option to access and

egress the NWRR. This would reduce the number of additional vehicles forecast to route through

these villages with the NWRR scheme in place, thereby mitigating a portion of the forecast impact of

the NWRR on Boughton and Moulton.

8.3.6. Figure 8-1 below (drawing NWRR-WSP-51505-001) shows the approximate locations of the

proposed traffic calming measures.

Figure 8-1 – Locations of Traffic Calming Measures proposed in Boughton & Moulton

8.3.7. The sections below describe the forecast impact of the two individual elements of Mitigation Scheme

1.

TRAFFIC CALMING SCHEME A

8.3.8. A “Give way to oncoming vehicles” pinch point feature (see Figure 8-2 below), also known as a Priority

Give way with pinch point, is where the road is narrowed to one lane for a short distance, sometimes

up to 10 metres. Priority signage and road markings are implemented to allow priority to vehicles from


one direction. By implementing this measure, free-flow of vehicles travelling in one direction can be

restricted by oncoming traffic. This has the impact, particularly at busy times, of slowing traffic and

reducing the convenience of a route.

Figure 8-2 - A “Give way to oncoming vehicles” pinch point feature

8.3.9. Therefore, installing a “Give way to oncoming vehicles” pinch point feature on the section of Vyse

Road between Harborough Road and Howard Lane may serve to discourage vehicles from routing on

this section of this road as it would slow traffic, increase journey times and make it a generally less

convenient route to navigate. This should discourage longer strategic trips (e.g. trips to and from the

NWRR) from routing on these roads resulting in less vehicles using this route which would help

mitigate the increase of vehicle traffic forecast on these roads as a result of the NWRR.

8.3.10. It is proposed that the “Give way to oncoming vehicles” pinch point feature will be located within sight

of the A508 but far enough away to reduce the likelihood of vehicles backing up on to the A508

Harborough Road / Brampton Lane / Vyse Road Roundabout.


TRAFFIC CALMING SCHEME B

8.3.11. There is currently a “Give way to oncoming vehicles” pinch point feature located outside the entrance

of Boughton Primary School where the pavement is built out on both sides of the road so the

carriageway narrows to a single lane width (see Figure 8-3 below). Vehicles travelling eastbound

have priority over those travelling westbound.

Figure 8-3 - The “Give way to oncoming vehicles” pinch point feature located outside the

entrance of Boughton Primary School facing westbound

8.3.12. Enhancing the “Give way to oncoming vehicles” pinch point feature located outside the entrance of

Boughton Primary School by narrowing the carriageway at the restriction as far as practical would

likely discourage drivers from routing through Boughton for longer strategic trips (e.g. trips to and from

the NWRR) as vehicles would be forced to slow down when navigating through it which would disrupt

their journey and lengthen journey time. Consideration could also be given to lengthening the “Give

way to oncoming vehicles” pinch point feature along the road which will lengthen the amount of time

a vehicle takes to travel through the feature, lengthening the time it has to travel at a slower speed

and thus lengthening their journey time and the journey time of any oncoming vehicles waiting to

proceed. This would reinforce the perception that the roads through Boughton are not an appropriate

through route, thereby helping mitigate the increase number of vehicles forecast to route through

Boughton as a result of building the NWRR.



8.4.1. The results from the junction capacity assessments (refer to Table 7-3) suggest that the A508

Harborough Road / Brampton Lane / Vyse Road Roundabout (J3) is forecast to operate over capacity

and experience congestion and delays in both the Do Minimum and Do Something 2031 future year

scenarios. As a result, the following measures have been proposed to mitigate the forecast impact of

the proposed scheme:

The flare length of the entry arm on Brampton Lane has been increased from 4.5 metres to 60.2

metres to allow for a dedicated right-hand lane into Far Barrows;

The entry width of the entry arm on Brampton Lane has been increased from 5.8 metres to 8.0

metres to allow for dedicated left / straight-ahead and right turn lanes;

A short left-turn flare lane has been added to the Vyse Road approach arm by widening the entry

width from 5.2 metres to 9.0 metres; and

The approach road half width of the entry arm on Vyse Road with has been increased from 2.8

metres to 4.0 metres.

8.4.2. Both entry improvements are considered to be the maximum possible within the highway without land

acquisition. Whilst it would appear to be possible to lengthen the proposed flare on the Vyse Road

approach even further along the southern verge, in practice this would result in steep verge crossings

for the existing private driveways along this side of Vyse Road as well as reducing the visibility splays

currently enjoyed by each driveway, which would raise road safety concerns. It is therefore considered

that this scheme is the maximum realistic mitigation scheme that can cost-effectively achieved at this

location.

8.4.3. The mitigated design is shown on Drawing No: NWRR-WSP-HGN-0000-SK-CH-00001 P03,

contained within Appendix K.

8.4.4. The mitigation scheme for the A508 Harborough Lane / Brampton Lane / Vyse Road Roundabout has

been modelled in Junctions 9 for the 2021 and 2031 future year scenarios for both peak hours. The

mitigated roundabout has been modelled with a flat traffic profile for each movement, rather than a

synthesised peak (as per the existing junction). This is appropriate in this case, given that the network

is likely to experience increased congestion in 2021 and 2031, thereby flattening traffic profiles across

the network. The results are provided in Table 8-1 below, with the full Junctions 9 output report is

provided in Appendix H.

Table 8-1 - A508 Harborough Road / Brampton Lane / Vyse Road Mitigated Roundabout

AM PM

Queue (PCU)

Delay (s/PCU)

RFC Queue (PCU)

Delay (s/PCU)

RFC

2021 DS

Arm A – Vyse Road (E) 1.2 9.09 0.54 4.5 22.97 0.82




2031 DS


Arm A – Vyse Road (E) 3.6 21.65 0.79 16.5 69.84 0.96




8.4.5. The results summarised in Table 8-1 above indicate that the mitigation scheme for the A508

Harborough Lane / Brampton Lane / Vyse Road Roundabout operates within capacity in the 2021 Do

Something scenario. However, the junction starts to operate over-capacity in the 2031 Do Something

scenario, albeit the mitigated layout remains within theoretical capacity, with RFC values under 1.00.

8.4.6. The mitigated layout performs better overall when compared to the existing layout in the 2031 Do

Minimum scenario, especially on the Vyse Road and Brampton Lane arms. The RFC value on Vyse

Road has reduced from 1.10 in the Do Minimum scenario to 0.96 in the Do Something scenario in the

PM peak hour. Similarly, the RFC value on Brampton Lane has decreased from 1.03 in the Do

Minimum scenario to 0.98 in the Do Something scenario in the AM peak hour. The mitigated layout

therefore provides a betterment to the existing junction in the 2031 future year scenario as the

roundabout is able to operate within theoretical capacity.

8.4.7. Although the mitigated layout provides an overall betterment to the operation of the junction, the A508

Harborough Road (N) arm performs slightly worse when compared to the existing junction in the 2031

Do Minimum scenario. The RFC value on the A508 Harborough Road (N) has increased from 0.57 to

0.90 in the AM peak hour and 0.37 to 0.55 in the PM peak hour. However, given that the mitigated

junction performs better overall than the existing layout, the mitigation scheme should be considered

acceptable.

8.4.8. Overall, the fact that the operation of the junction following the NWRR provides a betterment to the

existing junction, as well as the wider benefits of the scheme along the network and the proposed

mitigation scheme is the maximum cost-effective mitigation which can realistically be achieved, the

proposed mitigation scheme should be considered appropriate for mitigating the impacts of the

proposed NWRR scheme.



Harlestone Road / New Sandy Lane / York Road Roundabout (J7) is forecast to operate over capacity

in both the Do Minimum and Do Something 2031 future year scenarios. As a result, the following

measures have been proposed to mitigate the forecast impact of the proposed scheme:

The left-side flare lane on Harlestone Road South has been lengthened from 16 metres to 50

metres;

The entry width on New Sandy Lane has been slightly increased from 7.2 metres to 8 metres and

the flare length has been increased from 17 metres to 30 metres;

All exit arms of the junction are marked as two lane exits; and

Lane markings provided on the circulatory carriageway of the roundabout.

8.5.2. The mitigated design is shown on Drawing No: NWRR-WSP-HGN-0000-SK-CH-00003 P02,

contained within Appendix K.


8.5.3. The mitigation scheme for the A428 Harlestone Road / New Sandy Lane / York Road Roundabout

has been modelled in Junctions 9 for the 2021 and 2031 future year scenarios for both peak hours.

The mitigated roundabout has been modelled with a flat traffic profile for each movement, rather than

a synthesised peak (as per the existing junction). This is appropriate in this case, given that the

network is likely to experience increased congestion in 2021 and 2031, thereby flattening traffic

profiles across the network.

8.5.4. The results are provided in Table 8-2 below, with the full Junctions 9 output report is provided in

Appendix H.

Table 8-2 - A428 Harlestone Road / New Sandy Lane / York Road Mitigated Roundabout

AM PM

Queue (PCU)

Delay (s/PCU)

RFC Queue (PCU)

Delay (s/PCU)

RFC

2021 DS

Arm A – York Way (E) 2.4 8.27 0.71 3.9 13.07 0.80




2031 DS

Arm A – York Way (E) 3.7 12.39 0.79 6.2 19.48 0.86




8.5.5. The results summarised in Table 8-2 above show that the mitigation scheme for the A428 Harlestone

Road / New Sandy Lane / York Road Roundabout operates within capacity in the 2021 future year

scenario during both peak. The junction would operate close to its theoretical capacity with an RFC of

0.94 on the New Sandy Lane arm during the AM peak hour in the 2031 Do Something scenario.

Additionally, the York Way arm just slightly exceeds practical capacity with an RFC of 0.86 in the PM

peak hour in the 2031 Do Something scenario.

8.5.6. However, the mitigated layout of the junction performs much better than if no interventions were

proposed which therefore provides a betterment, albeit a similar level of operation compared to the

2031 Do Minimum Scenario. Similarly to the above, this coupled with the wider benefits as a result of

the NWRR scheme, means that the measures proposed at this junction should be considered

appropriate for mitigating the impact of the proposed scheme.


8.6.1. As explained in paragraph 8.3.4, measures have been proposed at the A508 Harborough Road /

A5076 Holly Lodge signalised junction (J4) to improve capacity and encourage vehicles to use this

junction as oppose to routing through the villages of Boughton and Moulton to access and egress the

NWRR, following traffic calming measures contained within Mitigation Scheme 1.


8.6.2. The following measures have been proposed to the A508 Harborough Road / A5076 Holly Lodge

signalised junction:

The left turn lane on the A5076 Holly Lodge Drive is lengthened by 50m from 40m to 90m; and

The left turn lane on the A508 Harborough Road North is lengthened by 50m from 70m to 120m.

8.6.3. The above changes are illustrated on Drawing No: NWRR-WSP-HGN-0000-SK-CH-00002, contained

within Appendix K.

8.6.4. The mitigation scheme for the A508 Harborough Road / A5076 Holly Lodge Drive signalised junction

has been modelled in LinSig for the 2021 and 2031 future year scenarios for both peak hours. The

junction operates on a single controller and stage stream, with both traffic and pedestrian phases

using MOVA. The LinSig model has been run with a cycle time of 120 seconds for each scenario.

8.6.5. The results are provided in Table 8-3 below, with the full LinSig output report provided in Appendix

H.

Table 8-3 - A508 Harborough Road / A5076 Holly Lodge Mitigated Signalised Junction


AM PM

DoS Mean Max

Queue (PCU) DoS


2021 DS

1/2+1/1 Holy Lodge Drive Left Right

54.9% 10.1 74.4% 16.9

2/1 Harborough Road S Ahead

50.8% 9.8 74.4% 18.3

2/2 Harborough Road S Right

43.1% 4.6 27.7% 3.1

3/1 Harborough Road N Left

50.4% 8.4 46.9% 7.4

3/2 Harborough Road N Ahead

53.7% 10.2 42.0% 8.0


2031 DS

1/2+1/1 Holy Lodge Drive Left Right

60.5% 11.6 76.2% 17.4

2/1 Harborough Road S Ahead

44.5% 7.6 77.4% 20.1

2/2 Harborough Road S Right

59.5% 6.1 38.7% 5.1

3/1 Harborough Road N Left

60.5% 11.6 57.8% 10.8

3/2 Harborough Road N Ahead

59.7% 10.0 30.3% 5.5



8.6.6. As can be seen above, the results show that the updated junction works within capacity during both

future year scenarios in both peak hours. Table 8-4 below compares the PRC results from Table 8-3

above with the results presented in Table 7-4 for the existing junction layout with the same traffic

flows.

Table 8-4 - Comparison of PRC Values in Existing & Mitigated Layout

Scenario Existing Layout Mitigated Layout

2021 AM Peak 26.4% 63.9%

2021 PM Peak 11.3% 21.0%

2031 AM Peak 20.3% 48.8%

2031 PM Peak 4.4% 16.3%

8.6.7. As shown in Table 8-4 above, the mitigation scheme proposed provides a betterment to the existing

junction in all scenarios during both peak hours as the PRC values are much higher in the proposed

mitigated layout than the existing. This betterment will serve to accommodate any diverted traffic due

to the implementation of the traffic calming measures included as part of Mitigation Scheme 1 (traffic

calming through Boughton and Moulton).

8.7 SUMMARY

8.7.1. This Chapter has provided details on the off-site mitigation measures proposed as part of the scheme

and includes the results of junction capacity assessments where relevant. The proposed mitigation

measures, the locations of and necessity for which has been agreed with NH’s Development Control

team, are listed below:

Mitigation Scheme 1: Traffic calming improvements in the villages of Moulton and Boughton;

Mitigation Scheme 2: Capacity mitigation improvements at the A508 Harborough Road /

Brampton Lane / Vyse Road Existing Roundabout (J3);

Mitigation Scheme 3: Capacity mitigation improvements at the A428 Harlestone Road / New

Sandy Lane / York Road Roundabout (J7); and




8.7.2. Following discussion with Northamptonshire Highways’ Road Safety Team and Highways Engineering

team, it is proposed that Mitigation Scheme 1 will consist of the introduction of a priority give-way

pinch-point feature on Vyse Road and the enhancement of an existing priority give-way pinch-point

feature near Boughton primary School. It is considered that these features will make the villages less

attractive as a through route for vehicles seeking to travel to and from the proposed NWRR.

8.7.3. Mitigation Scheme 2, at the A508 Harborough Road / Brampton Lane / Vyse Road Roundabout,

consists of flare length, approach road half width and entry width improvements to the Brampton Lane

and Vyse Road arms. The level of improvement proposed is the maximum which can be realistically

and cost effectively achieved within highway land. The modelling results of the proposed mitigation

scheme suggest that in 2031, the junction will operate within theoretical capacity which is a betterment

compared to the existing Do Minimum scenario. As such, it is considered that the mitigation scheme

is acceptable for mitigating the impacts of the proposed scheme.


8.7.4. Mitigation Scheme 3, at the A428 Harlestone Road / New Sandy Lane / York Road Roundabout,

consists of flare improvements on Harlestone Road south and New Sandy Lane, as well as lining

amendments to the circulatory carriageways and exits. The modelling results suggest that in the 2031

Do Something scenario, the mitigated junction operates close to theoretical capacity on the New

Sandy Lane arm and exceeds practical capacity on the York Way arm. This level of operation can be

considered acceptable as the mitigation layout performs much better than if no interventions were

proposed and a similar level of operation to the Do Minimum scenario, as well as the significant wider

benefits that the proposed NWRR will bring.

8.7.5. Proposed Mitigation Scheme 4, at the A508 Harborough Road / A5076 Holly Lodge Drive Signalised

Junction, consists of lengthened left turn lanes on the Holly Lodge Drive and A508 Harborough Road

North approaches to the junction. The modelling results indicate that the scheme would increase the

available spare capacity at the junction, thereby making capacity available for a level of traffic which

could be diverted through the junction as a result of Mitigation Scheme 1.

8.7.6. It is concluded that the proposed package of mitigation schemes, when considered alongside the

wider benefits of the scheme, will mitigate the impact of the NWRR such that the traffic impact should

not be judged severe in terms of NPPF.


9 MONITOR & MANAGE STRATEGY

9.1 INTRODUCTION

9.1.1. Following the results of the junction capacity assessments undertaken in Chapter 7, this section of

the report introduces the Monitor and Manage Strategy which is proposed at several junctions which

were identified as being adversely impacted by the proposed scheme and were not mitigated in the

previous chapter.

9.1.2. This Monitor and Manage Strategy is proposed to avoid short-term improvement schemes which may

have limited longevity due to various unknown variables which can make any such schemes abortive.

These junctions which are adversely impacted by the proposed scheme are influenced by factors such

as the phasing of committed development traffic, committed schemes or additional infrastructure,

which could influence how traffic is distributed over time. Therefore, the performance of these junctions

will be observed by NCC once the proposed scheme is operational, with traffic counts being

undertaken annually to understand the impact of the reassignment of traffic prior to delivering any

mitigation scheme.

9.1.3. The Monitor and Manage Strategy is proposed at the following junctions:


A508 Harborough Road / Brampton Lane Priority Junction; and

New Sandy Lane / Berrywood Road / Roman Road / Sandy Lane Proposed Roundabout.

9.1.4. The details of the schemes that could be delivered as part of the Monitor and Manage Strategy are

explained in more detail below.

9.2 PROPOSED MONITOR & MANAGE STRATEGY

9.2.1. As demonstrated in Chapter 7, comparisons of the modelling results for the Do Minimum and the Do

Something scenarios has highlighted the following potential issues would likely occur and be

attributable to the proposed scheme being built:

J1: Vehicles would experience significant congestion and delay at the A508 Harborough Road /

Pitsford High Street Priority Junction, particularly on the A508 Harborough Road South as there is

no stacking capacity for vehicles to turn right;


Brampton Lane Priority Junction, particularly on the A508 Harborough Road North as there is no

stacking capacity for vehicles to turn right; and

J8: Vehicles would experience significant congestion and delay at the Roman Road / New Sandy

Lane / Berrywood Road / Sandy Lane Proposed Roundabout, particularly on the Berrywood Road

and New Sandy Lane arms of the junction

9.2.2. In light of the above, potential mitigation options have been investigated in the event that mitigation

would be required for the above junctions. Indicative layouts for potential mitigation schemes have

been produced to highlight measures which could be implemented if mitigation were to be required

following the monitor and manage approach.

9.2.3. The following sub-sections details the potential mitigation schemes designed to address the capacity

issues experienced as a result of the proposed scheme at the junctions identified above.


9.3 J1: A508 HARBOROUGH ROAD / PITSFORD HIGH STREET PRIORITY

JUNCTION


Harborough Road / Pitsford High Street priority junction is forecast to operate over capacity and

experience congestion and delays in both the 2031 Do Something future year scenario. This is likely

due to queueing as there is no stacking capacity for vehicles to turn right, therefore one PCU can

block the junction, resulting in queues on the major arm.

9.3.2. Mitigation is not proposed at this current time because it is considered that delivering an improvement

scheme at this location will increase capacity, thereby allowing more traffic to travel through the

junction, encouraging more traffic through the villages of Boughton and Moulton. Additionally, the

future year traffic flows are dependent on committed developments and highway infrastructure coming

forward in the area which will also have an influence on future travel patterns. For instance, the NWRR

will form part of a longer-term strategy to deliver a route from the A4500 near the M1 Junction 16 and

the A43 north of Northampton, creating the Northampton Northern Orbital Route (NNOR), illustrated

in Figure 5-1 (above). The introduction of the NNOR would have further impact on the traffic flows

identified at this junction which could render any short-term improvements abortive. In light of this, it

has been determined that a Monitor and Manage Strategy is better suited at this location.

9.3.3. Despite the above, a potential mitigation option has been investigated in the event that mitigation

would be required. An indicative layout of a potential mitigation scheme is shown in Drawing NWRR-

WSP-HGN-0000-SK-CH-00006 P01, contained within Appendix K. The indicative layout shows the

addition of a right turn lane with the storage capacity of more than 2 PCUs on the A508 Harborough

Road which can be delivered within the extent of the Highway Boundary.

9.3.4. However, the junction operation should be observed once the scheme is opened to traffic, with traffic

counts undertaken annually to understand the impact of the reassignment of traffic prior to delivering

any mitigation scheme.

9.4 J2: A508 HARBOROUGH ROAD / BRAMPTON LANE PRIORITY

JUNCTION

9.4.1. The results from the junction capacity assessments (refer to Table 7-2) suggest that the junction

performs worse in the 2031 Do Something scenario when the proposed scheme is introduced. This is

likely due to queueing as there is no stacking capacity for vehicles to turn right, therefore one PCU

can block the junction, resulting in queues on the major arm.

9.4.2. As explained above, mitigation is not proposed at this current time because doing so would likely

increase capacity and encouraging more trips through the villages of Boughton and Moulton.

Additionally, the future year traffic flows are dependent on committed developments and highway

infrastructure (i.e. NNOR) coming forward in the area which will have an influence on future travel

patterns. It has therefore been determined that a Monitor and Manage Strategy is better suited at this

location.

9.4.3. A potential mitigation option has been investigated in the event that mitigation would be required. An

indicative layout of a potential mitigation scheme is shown in Drawing NWRR-WSP-HGN-0000-SK-

CH-00006 P01, contained within Appendix K. The indicative layout shows the addition of a right turn


lane with the storage capacity of more than 2 PCUs on the A508 Harborough Road which can be

delivered within the extent of the Highway Boundary.




9.5 J8: ROMAN ROAD / NEW SANDY LANE / BERRYWOOD ROAD / SANDY

LANE PROPOSED ROUNDABOUT

9.5.1. The results from the junction capacity assessments (refer to Table 7-10) suggest that the junction

performs worse in the 2031 Do Something scenario when the proposed scheme is introduced,

although no mitigation is currently proposed.

9.5.2. Mitigation measures are not proposed at this current time because it is understood that there are two

Sustainable Urban Extensions (SUE) in the vicinity of the proposed roundabout. These include the

Norwood Farm development (who are implementing the planned improvement scheme) and

Northampton West. The planned improvement scheme accommodates the development traffic from

both SUEs. It should be noted that both these developments will have a larger traffic impact than the

proposed scheme considering their proximity to the junction. Therefore, proposing a condition to

deliver a mitigation scheme on top of the already identified planned improvement prior to the opening

of the NWRR is not justified at this stage.

9.5.3. In addition to the above, the travel patterns and phasing of these developments will have an impact

on the operation of the junction. However, this cannot be determined until both schemes are built out

and operational. The future year traffic flows used in the junction capacity assessments have been

derived from the NSTM which assumes that both developments will be built to capacity by 2021. In

reality, this is unlikely to be the case and therefore it is suggested that this junction be included in the

Monitor and Manage Strategy prior to implementing any design changes.

9.5.4. Despite the above, a potential mitigation option has been investigated in the event that mitigation

would be required. The measures which can be delivered within the extent of the Highway Boundary

include:

Increasing the flare length on the entry arm of Berrywood Road East to 25m; and

Increasing the entry width on the entry arm of Sandy Lane to 10m to allow for dedicated left /

straight-ahead and right turn lanes, as well as increasing the flare length to 30m.

9.5.5. An indicative layout of a potential mitigation scheme is shown in Drawing NWRR-WSP-HGN-0000-

SK-CH-00007 P01, contained within Appendix K.




9.6 SUMMARY

9.6.1. This chapter provides details of the Monitor and Manage Strategy to be applied for the three junctions

assessed in the TA. Indicative layouts of the proposed scheme are also provided. However, it is

suggested that the junctions should be monitored once the scheme is operational, with traffic counts


undertaken annually to understand the operation of reassigned traffic prior to implementing any

mitigation schemes.


10 SUMMARY & CONCLUSIONS

10.1.1. This Transport Assessment (TA) has been prepared to support a planning application for a new relief

road proposed to the north-west of Northampton called the North-West Relief Road (NWRR). The

road proposed is of single carriageway standard, with the capacity to be upgraded to dual carriageway

in the future. It will join to the existing road network at the A5199 Northampton Road via a roundabout

to the north and at the A428 Harlestone Road / New Sandy Lane / York Way Roundabout to the south.

The northern section of the NWRR (approximately 1.61 km in length) is being delivered by NCC and

is the section of road that is the subject of this TA.

10.1.2. Chapter 3 demonstrates that the proposed scheme is supported by and adheres to both national and

local transport related policy and guidance.

10.1.3. Chapter 4 demonstrates that the proposed scheme caters for Non-Motorised Users (NMUs), including

pedestrians, cyclists and horse-riders, by incorporating a range of suitable NMU facilities within the

design of the proposed scheme. The chapter also outlined the conditions on Northampton’s Roads as

reported in the Northamptonshire Strategic Transport Model (NSTM); in turn validated and calibrated

against observed traffic flows in 2015.This highlighted several corridors and locations in the study area

where existing traffic volumes were leading to congestion and delay. These included:

A43 Lumbertubs Way;



A4500 Weedon Road; Harlestone Road (The Bramptons); and

Mill Lane;

10.1.4. Chapter 5 detailed the different aspects of the proposed scheme, as well as the context as to why the

scheme is needed in relation to the Dallington Grange development. This chapter also described the

two access junctions proposed, as well as the NMUs facilities proposed within the design of the

scheme.

10.1.5. Chapter 6 assessed the impact of the proposed scheme on the operation of the local highway

network, as well as detailing the scheme’s wider benefits. Analysis of the NSTM indicated that the

proposed scheme provides benefits to Northampton’s road users and residents. It will relieve traffic

issues already present in the 2015 base year on road corridors used for east-west trips in

Northampton. The proposed scheme will also provide benefit along the minor roads that weren’t

designed for heavy traffic volumes, or those utilised as alternative ‘rat-run’ routes to avoid congested

corridors into Northampton. These benefits are spread across the town and key areas include:

A43 Lumbertubs Way;



A4500 Weedon Road;


Harlestone Road (The Bramptons) and

Mill Lane.


10.1.6. The proposed scheme will also provide additional infrastructure capacity to support movements

generated by forecast development and growth in the region. The key locations and corridors which

showed a reduced 2031 traffic volume as a result of the NWRR included:

Harlestone Road West of the New Sandy Lane Roundabout;

A508 Kingsthorpe Road / Harborough Road;




Eastern Avenue.

10.1.7. Additionally, analysis of the wider benefits of the NWRR include:

A reduction in traffic flows on a number of significant links and junctions in Northampton when

compared to the Do Minimum case;

A very strong business case with a high Benefit/Cost Ratio (BCR) which demonstrates that the

savings, predominantly to travel time, outweigh the cost of delivering the scheme by 7 times, a very

high return for a transport scheme;

Additional capacity on the transport network to support housing growth targets; and

Additional resilience to the Northampton highway network when disruption arises from time to time,

such as planned roadworks, accidents or other foreseen and unforeseen events.

10.1.8. Chapter 7 compared the modelling results for the Do Minimum and the Do Something scenarios at

individual junctions. The results of the junction capacity assessments identified that the following

capacity issues would likely occur and be attributable to the proposed scheme:

Increased volume of vehicle traffic routing through the villages of Moulton and Boughton;


Pitsford High Street Priority Junction, particularly on the A508 Harborough Road South as there is

no stacking capacity for vehicles to turn right;


Brampton Lane Priority Junction, particularly on the A508 Harborough Road North as there is no

stacking capacity for vehicles to turn right;


Brampton Lane / Vyse Road Existing Roundabout, particularly on the Vyse Road and Brampton

Lane arms of the junction;

J7: Vehicles would experience significant congestion and delay at the A428 Harlestone Road /

New Sandy Lane / York Road Roundabout; and

J8: Vehicles would experience significant congestion and delay at the Roman Road / New Sandy

Lane / Berrywood Road / Sandy Lane Proposed Roundabout, particularly on the Berrywood Road

and New Sandy Lane arms of the junction.

10.1.9. Chapter 8 identified that the following mitigation measures would be required to mitigate the forecast

traffic impact of the proposed scheme:


Mitigation Scheme 2: Capacity improvements at A508 Harborough Road / Brampton Lane /

Vyse Road Roundabout (J3);


Mitigation Scheme 3: Capacity improvements at A428 Harlestone Road / New Sandy Lane /

York Road Roundabout (J7); and




10.1.10. Chapter 9 addressed the remaining junctions which were identified as being adversely impacted by

the proposed scheme and have been included in the Monitor and Manage Strategy. Indicative layouts

for potential mitigation schemes have been produced to highlight measures which could be

implemented if mitigation were to be required following the monitor and manage approach. The

junctions included in the Monitor and Manage Strategy are:


J2: A508 Harborough Road / Brampton Lane Priority Junction; and

J8: New Sandy Lane / Berrywood Road / Roman Road / Sandy Lane Proposed Roundabout.

10.1.11. Monitoring of traffic flows at these junctions are suggested after the scheme is operational, with traffic

counts undertaken annually (by NCC) to understand the impacts of any reassignment of traffic prior

to the delivery of any mitigation measures at these locations.

10.1.12. Overall, this Transport Assessment has shown that the proposed scheme provides a benefit to road

users across Northampton and the surrounding network. The proposed scheme is expected to relieve

existing traffic congestion at certain locations in Northampton, as well as provide additional

infrastructure capacity to support movements generated by forecast development and growth within

the region. However, where the NWRR is forecast to have some negative traffic impacts, the following

should be considered when assessing the proposed scheme:

Any negative impacts caused as a result of the proposed scheme should be considered in the

context of the wider traffic benefits across the network as a whole;

The proposed scheme will create a balanced network of vehicles using existing and the new

infrastructures proposed which will have a positive impact overall; and

Any negative impacts caused as a result of the proposed scheme can be mitigated where

appropriate or included in the Monitor and Manage Strategy.

10.1.13. Taking account of the above, this Transport Assessment has shown that the proposed scheme

provides an overall net benefit to the highway network and any negative localised impacts caused as

a result of the scheme can be satisfactorily mitigated. As such, this Transport Assessment concludes

that the proposed scheme is acceptable in terms of highways and transport impact.