ROAD PPT

NRA TD 27/07NRA TD 27/07CROSSCROSS--SECTION AND HEADROOMSECTION AND HEADROOM

DMRB Vol 6 – File 4 0

TABLE OF CONTENTS OF TD 27TABLE OF CONTENTS OF TD 27

IntroductionIntroduction Design PrinciplesDesign Principles CrossCross--Sections on Open RoadsSections on Open Roads CrossCross--Sections at StructuresSections at Structures Headroom at StructuresHeadroom at Structures Headroom at StructuresHeadroom at Structures References References

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1.01.0 INTRODUCTIONINTRODUCTION

1.1 1.1 General General This This standard outlines the design principals and factors which standard outlines the design principals and factors which shouldshould

b id d b D i i l ti db id d b D i i l ti d ti dti dbe considered by Designers in selecting road crossbe considered by Designers in selecting road cross--sections and sections and headroomheadroom..

The standard The standard applies to all National Roads and side roads diverted as applies to all National Roads and side roads diverted as part of a National Road Scheme.part of a National Road Scheme.

Where used for a Local Road Scheme, refer to the relevant Road Where used for a Local Road Scheme, refer to the relevant Road Authority for their requirements.Authority for their requirements.

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1.2 1.2 Important Definitions (Clause 1.11)Important Definitions (Clause 1.11) Central Reserve : Central Reserve : -- The area which separates the carriageway of a The area which separates the carriageway of a

dualdual carriageway andcarriageway and includesincludes the widths of offside hard stripsthe widths of offside hard stripsdualdual carriageway and carriageway and includesincludes the widths of offside hard strips.the widths of offside hard strips. Cross Cross Section : Section : -- The road cross section incorporates all elementsThe road cross section incorporates all elements

between the boundaries including : between the boundaries including : Carriageways including cycle lanesCarriageways including cycle lanes Carriageways including cycle lanesCarriageways including cycle lanes Central Reserve if anyCentral Reserve if any Separation zonesSeparation zones HardHard shoulders and hard stripsshoulders and hard strips Hard Hard shoulders and hard stripsshoulders and hard strips Verges including footpaths, cycle tracksVerges including footpaths, cycle tracks Cutting or embankment slopesCutting or embankment slopes

BB d kid ki BermsBerms and working spaces and working spaces D2AP :D2AP :-- Dual two lane all purpose road.Dual two lane all purpose road. S2 : S2 : -- Two lane single carriageway with carriageway lane width of up Two lane single carriageway with carriageway lane width of up

to 3 65mto 3 65mto 3.65m.to 3.65m.

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1.2 1.2 Important Definitions (Clause 1.11) Important Definitions (Clause 1.11) –– Cont.Cont.

Mainline Mainline –– The The c/w carrying the main flow of traffic.c/w carrying the main flow of traffic.

Nearside Nearside –– LeftLeft hand side of vehicle when viewing a forward vehicle hand side of vehicle when viewing a forward vehicle from behind.from behind.

T 1 D l /T 1 D l / A di id d ll d ith t l i hA di id d ll d ith t l i h Type 1 Dual c/w Type 1 Dual c/w –– A divided all purpose road with two lanes in each A divided all purpose road with two lanes in each direction constructed to the geometric standards of NRA TD9 and direction constructed to the geometric standards of NRA TD9 and TD22. TD22.

Type 2 Dual c/w Type 2 Dual c/w –– A divided all purpose road with two lanes in each A divided all purpose road with two lanes in each direction constructed to the geometric standards of NRA TD10.direction constructed to the geometric standards of NRA TD10.

Type 3 Dual c/wType 3 Dual c/w A divided road with two lanes in one direction oneA divided road with two lanes in one direction one Type 3 Dual c/w Type 3 Dual c/w –– A divided road with two lanes in one direction, one A divided road with two lanes in one direction, one lane in the other direction, constructed to the geometric standards to lane in the other direction, constructed to the geometric standards to NRA TD10.NRA TD10.

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1.2 1.2 Important Definitions (Clause 1.11) Important Definitions (Clause 1.11) –– Cont.Cont. Roads Roads : Urban and Rural : : Urban and Rural :

Urban Roads Urban Roads –– in a built up area and either in a built up area and either a)a) single single carriageway with a speed limit of carriageway with a speed limit of 60kph 60kph or or less; or less; or b)b) dualdual carriageway with speed limit ofcarriageway with speed limit of 80kph80kph or lessor lessb)b) dual dual carriageway with speed limit of carriageway with speed limit of 80kph 80kph or less. or less. Rural Roads : All other Roads:Rural Roads : All other Roads:

Verge : Verge : -- The part of the road cross section alongside a The part of the road cross section alongside a gg p gp gcarriageway but not including embankment or cutting slopes carriageway but not including embankment or cutting slopes (includes the width of hard strips but excludes hard shoulders (includes the width of hard strips but excludes hard shoulders widths).widths).

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2.02.0 DESIGN PRINCIPLESDESIGN PRINCIPLES

2.1 2.1 GeneralGeneral The underlying principal is that Designers are given the maximum choice, so The underlying principal is that Designers are given the maximum choice, so

that there is flexibility to develop layout options that will meet NRAthat there is flexibility to develop layout options that will meet NRA objectives objectives (Clause 2.1). (Clause 2.1).

Designers Designers should balance considerations of : should balance considerations of : -- SafetySafety Environmental ImpactEnvironmental Impact Environmental ImpactEnvironmental Impact CostCost BuildabilityBuildability of the of the Road Elements Road Elements Operation and Operation and Maintenance Maintenance Ope at o a dOpe at o a d a te a cea te a ce Other Other Design Design ConstraintsConstraints Health and Safety Health and Safety ResponsibilitiesResponsibilities

The The Designer is Designer is notnot given choices over the widths of running lanes, hard given choices over the widths of running lanes, hard t i d h d h ld f ti l t f d A i ti it i d h d h ld f ti l t f d A i ti istrips, and hard shoulders for a particular type of road. Any variation is a strips, and hard shoulders for a particular type of road. Any variation is a

‘Departure’ (Clause 2.5). ‘Departure’ (Clause 2.5). Designer Designer does have flexibilitydoes have flexibility over the width of work space, over the width of work space, bermsberms, side , side

slopes,slopes, verges and central reserves although a reduction of verge or central verges and central reserves although a reduction of verge or central id hid h b l d i bl i i ill i R l ib l d i bl i i ill i R l ireserve widthreserve width below desirable minimum will require a Relaxation. below desirable minimum will require a Relaxation.

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2.02.0 DESIGN PRINCIPLESDESIGN PRINCIPLES

2.2 2.2 Design ProgressDesign Progress In In development of the road crossdevelopment of the road cross--section, the road pavement widths section, the road pavement widths

fi d I th idth hi h th D i h fl ibilit d idfi d I th idth hi h th D i h fl ibilit d idare fixed. In the widths which the Designer has flexibility, road side are fixed. In the widths which the Designer has flexibility, road side features will impact on the required widths such as : features will impact on the required widths such as : Location of Safety BarriersLocation of Safety Barriers –– could be could be significant.significant. Drainage, Drainage, DuctingDucting, , Services, Public Services, Public Lighting.Lighting. Provision of Provision of FootpathsFootpaths, , Cycle Cycle Tracks.Tracks.

P i i f D i t d L (P i i f D i t d L (D tD t l 2 14)l 2 14) Provision of Designated Lanes (Provision of Designated Lanes (Departures Departures as per clause 2.14).as per clause 2.14). BermsBerms, , Landscaping Landscaping Requirements.Requirements.

Requirements forRequirements for VisibilityVisibility on curved alignments and approaches toon curved alignments and approaches toRequirements for Requirements for VisibilityVisibility on curved alignments and approaches toon curved alignments and approaches tojunctions may necessitate wider crossjunctions may necessitate wider cross--section to accommodate section to accommodate widerwider verges and central Reserves (Clause 2.25 and TD 9).verges and central Reserves (Clause 2.25 and TD 9).

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3.03.0 CROSSCROSS--SECTIONS ON OPEN ROADSSECTIONS ON OPEN ROADS

(I.E. AWAY FROM STRUCTURES)(I.E. AWAY FROM STRUCTURES)3.1 3.1 GeneralGeneral Tables Tables 2, 3, 4 and 5 gives detailed2, 3, 4 and 5 gives detailed dimensions for the road dimensions for the road

pavements, verges and central reserves for National Roads both rural pavements, verges and central reserves for National Roads both rural and urban in the and urban in the open.open.

WideWide dual carriageways are dual carriageways are notnot to be used without NRA agreement to be used without NRA agreement (Clause 3.2).(Clause 3.2).

Cross section of a side road which is not a National Road should beCross section of a side road which is not a National Road should be Cross section of a side road which is not a National Road should beCross section of a side road which is not a National Road should beagreedagreed with thewith the NRA and the NRA and the relevant Road Authorityrelevant Road Authority (Clause 3.3).(Clause 3.3).

Any reduction or increase (except as per Clause 3.6) in paved Any reduction or increase (except as per Clause 3.6) in paved elementselements isis aa DepartureDeparture from standard (Clause 3 4)from standard (Clause 3 4)elementselements isis a a DepartureDeparture from standard (Clause 3.4).from standard (Clause 3.4).

Where there are different nearWhere there are different near--side edge treatment at merge / divergeside edge treatment at merge / divergelocations, the locations, the transition transition is to take place over the length of the taper is to take place over the length of the taper (Cl 3 10)(Cl 3 10)(Clause 3.10). (Clause 3.10).

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3.03.0 CROSSCROSS--SECTIONS ON OPEN ROADSSECTIONS ON OPEN ROADS

(I.E. AWAY FROM STRUCTURES)(I.E. AWAY FROM STRUCTURES)3.1 3.1 General Cont.General Cont. Where kerbs Where kerbs are used on are used on high speed high speed roads they are to have a roads they are to have a

maximum maximum height height of of 80mm 80mm and a 45 degree and a 45 degree splay splay (clause 3.61(clause 3.61).). Verge or central reserve widths greater that the desirable widths doVerge or central reserve widths greater that the desirable widths doVerge or central reserve widths greater that the desirable widths do Verge or central reserve widths greater that the desirable widths do

not require a not require a RelaxationRelaxation or or DepartureDeparture. Width . Width lessless than desirable shall than desirable shall be regarded as a be regarded as a DepartureDeparture. .

Urban Roads shall have raised verges (and kerbs) and footpaths asUrban Roads shall have raised verges (and kerbs) and footpaths as Urban Roads shall have raised verges (and kerbs) and footpaths as Urban Roads shall have raised verges (and kerbs) and footpaths as per Table 1.per Table 1.

For Urban Roads should also refer to NRA TD 9 and ‘Roads and For Urban Roads should also refer to NRA TD 9 and ‘Roads and Traffic in Urban Areas’ for further guidanceTraffic in Urban Areas’ for further guidanceTraffic in Urban Areas for further guidance.Traffic in Urban Areas for further guidance.

It should be noted that all the road cross sections are currently being It should be noted that all the road cross sections are currently being reviewed reviewed wrtwrt nonnon--motorised users.motorised users.

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REDUCED SINGLE CARRIAGEWAY (S2)REDUCED SINGLE CARRIAGEWAY (S2)

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STANDARD SINGLE CARRIAGEWAY (S2)STANDARD SINGLE CARRIAGEWAY (S2)

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TYPE 3 DUAL CARRIAGEWAYTYPE 3 DUAL CARRIAGEWAY

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TYPE 2 DUAL CARRIAGEWAY (D2AP)TYPE 2 DUAL CARRIAGEWAY (D2AP)

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TYPE 1 DUAL CARRIAGEWAY (D2AP)TYPE 1 DUAL CARRIAGEWAY (D2AP)

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STANDARD DUAL CARRIAGEWAY MOTORWAY STANDARD DUAL CARRIAGEWAY MOTORWAY (D2M) & (D2UM)(D2M) & (D2UM)

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WIDE DUAL CARRIAGEWAY MOTORWAY (D2M)WIDE DUAL CARRIAGEWAY MOTORWAY (D2M)

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SLIP ROADS, INTERCHANGE LINKS AND LOOPS: 1 LANESLIP ROADS, INTERCHANGE LINKS AND LOOPS: 1 LANE

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SLIP ROADS, INTERCHANGE LINKS AND LOOPS: 2 LANESLIP ROADS, INTERCHANGE LINKS AND LOOPS: 2 LANE

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DIVERGE SLIP ROADS ONLY 2 LANEDIVERGE SLIP ROADS ONLY 2 LANE

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4.04.0 CROSSCROSS--SECTIONS AT STRUCTURESSECTIONS AT STRUCTURES

4.1 4.1 GeneralGeneral NRA RCD 000/11 give crossNRA RCD 000/11 give cross--section details at bridgesection details at bridge structures. structures.

H id i b i d t i th t i i htH id i b i d t i th t i i htHowever widening maybe required to give the stopping sight However widening maybe required to give the stopping sight distances where the roaddistances where the road alignment is on a alignment is on a curvecurve (Clause 4.1).(Clause 4.1).

Variations of crossVariations of cross--section provision at bridges in closesection provision at bridges in close succession succession are to be avoided (Clause 4.2). are to be avoided (Clause 4.2).

Carriageway Carriageway widths, hard shoulder and hard strip widths are towidths, hard shoulder and hard strip widths are to be be maintained through or over structures (Clause 4.6 and 4.7). maintained through or over structures (Clause 4.6 and 4.7). g ( )g ( )

Width of Central Reserves applicable to the adjacent open roadWidth of Central Reserves applicable to the adjacent open roadsection should be continued through or over the structuresection should be continued through or over the structure..

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4.0 CROSS-SECTIONS AT STRUCTURES

4.1 4.1 General Cont.General Cont. Verges at Verges at UnderbridgesUnderbridges shall be raised (80mm maximum on high shall be raised (80mm maximum on high

d d ) ithd d ) ith idth T bl 6 ( i b t 0 6 didth T bl 6 ( i b t 0 6 dspeed roads) withspeed roads) with widths as per Table 6 (varying between 0.6m and widths as per Table 6 (varying between 0.6m and 2.0m) (Clause 4.13). 2.0m) (Clause 4.13).

Verges beneath Verges beneath OverbridgesOverbridges shall be not less than 2.0m. Where there shall be not less than 2.0m. Where there is an abutmentis an abutment adjacent to the carriageway, the face of the abutment adjacent to the carriageway, the face of the abutment is to be is to be at leastat least 4.5m from the4.5m from the edge of the road pavement. If the edge of the road pavement. If the bridge support is a pier closest to the road, the setbridge support is a pier closest to the road, the set--back to theback to the face of face of th i b 2 t i ith i b 2 t i ithe pier maybe 2 metres minimum. the pier maybe 2 metres minimum.

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CROSSCROSS--SECTIONS AT STRUCTURESSECTIONS AT STRUCTURES

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TABLE 6: VERGE WIDTHS ON UNDERBRIDGESTABLE 6: VERGE WIDTHS ON UNDERBRIDGES

Road Type Location Pedestrian Usage (see

Bridge Length

RaisedVerge WidthUsage (see

Paragraph 4.11)

Length m

Verge Width m

Motorway Nearside All 0 60Motorway Nearside Offside

--

AllAll

0.600.60

All-Purpose Road

Nearside RegularRegular

< 100>100

2.001 50Road Regular

Occasional>100

All1.501.50

Offside* All All 0.60

Note: * For bridges carrying NonNote: * For bridges carrying Non--National Roads it may be appropriate to treat one side as National Roads it may be appropriate to treat one side as the offside despite the road carrying twothe offside despite the road carrying two--way traffic. See paragraph 4.5. way traffic. See paragraph 4.5.

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5.05.0 HEADROOM AT STRUCTURESHEADROOM AT STRUCTURES

5.1 5.1 GeneralGeneral At At OverbridgesOverbridges and at other structures over a road, Table 7 givesand at other structures over a road, Table 7 gives the the

‘New ‘New Construction Construction Headroom’ and ‘Maintained Headroom’ varying Headroom’ and ‘Maintained Headroom’ varying between 5 03m and 5 7m (Clause 5 1)between 5 03m and 5 7m (Clause 5 1)between 5.03m and 5.7m (Clause 5.1). between 5.03m and 5.7m (Clause 5.1).

Additional Headroom is to be provided:Additional Headroom is to be provided: At At location of vertical sag curves (Table 8)location of vertical sag curves (Table 8) ToTo allow for deflection of the structure (Clauseallow for deflection of the structure (Clause 5 9)5 9) To To allow for deflection of the structure (Clauseallow for deflection of the structure (Clause 5.9)5.9) Where required Where required by Utility Companies.by Utility Companies.

Headroom requirements are the minimum Headroom requirements are the minimum –– greater headroom maygreater headroom maybe provided if it is economical and / or environmentally acceptablebe provided if it is economical and / or environmentally acceptablebe provided if it is economical and / or environmentally acceptable be provided if it is economical and / or environmentally acceptable (Clause 5.3).(Clause 5.3).

The The relevant standard headroom is to be provided overrelevant standard headroom is to be provided over:: The full pavement width (carriageway, hardThe full pavement width (carriageway, hard shoulder and or hard shoulder and or hard p ( g yp ( g y

strip). strip). The full verge width unless protected by a safetyThe full verge width unless protected by a safety fence (see fence (see

Clause 5.6 (e) andClause 5.6 (e) and Figure 1).Figure 1).Th f ll t l idthTh f ll t l idth The full central reserve width.The full central reserve width.

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TABLE 7 STANDARD HEADROOM TABLE 7 STANDARD HEADROOM AT AT STRUCTURESSTRUCTURES

TYPE OF STRUCTURE NEW CONSTRUCTION HEADROOM (M)

MAINTAINED HEADROOM (M)

Overbridges 5.30 5.03g

Footbridges and Sign / Signal Gantries 5.70 5.41

Free Standing Temporary Structures N/A 5.41

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FIGURE 1: HEADROOM AT STRUCTURESFIGURE 1: HEADROOM AT STRUCTURES

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GUIDANCE ON WHICH ROAD STANDARD TO USE

11 Strategic DecisionStrategic Decision Government Government has decided on certain minimum standards for certain has decided on certain minimum standards for certain

l t f th t k F l th N ti l D l tl t f th t k F l th N ti l D l telements of the network. For example, the National Development elements of the network. For example, the National Development Plan 2000 to 2006 contains a development strategy to develop the Plan 2000 to 2006 contains a development strategy to develop the major national primary routes to Galway, Limerick, Cork, Waterford major national primary routes to Galway, Limerick, Cork, Waterford and to the border north of Dundalk to motorway / high quality dualand to the border north of Dundalk to motorway / high quality dualand to the border north of Dundalk, to motorway / high quality dual and to the border north of Dundalk, to motorway / high quality dual carriageway standard in their entirety. This decision is aimed at carriageway standard in their entirety. This decision is aimed at providing a minimum level of service ‘C’ on the major national providing a minimum level of service ‘C’ on the major national primaries (i.e. average interprimaries (i.e. average inter--urban speed of 94kph on a dualurban speed of 94kph on a dualprimaries (i.e. average interprimaries (i.e. average inter urban speed of 94kph on a dual urban speed of 94kph on a dual carriageway and 105 kph on a motorway). This decision is based on carriageway and 105 kph on a motorway). This decision is based on national strategic considerations and not on traffic flows alone. national strategic considerations and not on traffic flows alone.

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GUIDANCE GUIDANCE ON WHICH ON WHICH ROAD STANDARD ROAD STANDARD TO USETO USE

22 Rural RoadsRural Roads Guidance Guidance for the layout features appropriate for various types offor the layout features appropriate for various types of rural rural

dd ti i i i T bl 4 f TD 9/07 (Clti i i i T bl 4 f TD 9/07 (Cl 6 2 f TD6 2 f TDroad crossroad cross--sections is given in Table 4 of TD 9/07 (Clausesections is given in Table 4 of TD 9/07 (Clause 6.2 of TD 6.2 of TD 9/07).9/07).

Table 4 gives Table 4 gives recommendations for each road type under : recommendations for each road type under : Traffic Capacity for LOS ‘DTraffic Capacity for LOS ‘D’ (may need to be verified)’ (may need to be verified) Access TreatmentAccess Treatment

J tiJ ti T t t t Mi R dT t t t Mi R d Junction Junction Treatment at Minor RoadsTreatment at Minor Roads Junction Treatment at Major Junction Treatment at Major RoadsRoads

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TABLE 4 FROM NRA TD 9: TABLE 4 FROM NRA TD 9: RECOMMENDED RURAL ROAD LAYOUTSRECOMMENDED RURAL ROAD LAYOUTS

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33 From the road scheme traffic studies the predicted design year AADT From the road scheme traffic studies the predicted design year AADT

fl ( ll t kfl ( ll t k 1515 f th f i ) h ldf th f i ) h ldflows (normally taken flows (normally taken as 15 as 15 years from the year of opening) should years from the year of opening) should not exceed the capacity for LOS ‘D’ for the selected road crossnot exceed the capacity for LOS ‘D’ for the selected road cross--section and category of road. The chosen road type using traffic section and category of road. The chosen road type using traffic flows should then be checked against the achievement offlows should then be checked against the achievement offlows should then be checked against the achievement of flows should then be checked against the achievement of recommended junction types, access treatment and environmental recommended junction types, access treatment and environmental impacts.impacts.

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44 UK DMRBUK DMRB The equivalent Table 4 in the UK TD 9/93 does not state any traffic The equivalent Table 4 in the UK TD 9/93 does not state any traffic

iti f th diff t diti f th diff t d ti Withi th d iti Withi th d icapacities for the different road crosscapacities for the different road cross--sections. Within the advicesections. Within the advicenote TA 46/97 in the UK Volume 5, recommended traffic flow ranges note TA 46/97 in the UK Volume 5, recommended traffic flow ranges for new Rural Road Links are listed in Table 2.1 for the year of for new Rural Road Links are listed in Table 2.1 for the year of opening These flow ranges are given so that the resulting chosenopening These flow ranges are given so that the resulting chosenopening. These flow ranges are given so that the resulting chosen opening. These flow ranges are given so that the resulting chosen road cross section can be economically assessed. This procedure road cross section can be economically assessed. This procedure has not been adopted by the NRA. has not been adopted by the NRA.

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55 URBAN ROADSURBAN ROADS As stated in Clause 6.3 of TD 9/07, it is not possible to tabulate As stated in Clause 6.3 of TD 9/07, it is not possible to tabulate

overall layoutoverall layout characteristics for Roads in urban areas in the samecharacteristics for Roads in urban areas in the sameoverall layoutoverall layout characteristics for Roads in urban areas in the samecharacteristics for Roads in urban areas in the sameway as for rural areas as the constraints of the existing urban fabric way as for rural areas as the constraints of the existing urban fabric will result in Designs tailored to meet the site specific requirementswill result in Designs tailored to meet the site specific requirements. . The capacity of the road scheme is likely to be controlled by the The capacity of the road scheme is likely to be controlled by the capacity of the junctions rather than the capacity of the linkcapacity of the junctions rather than the capacity of the linkcapacity of the junctions rather than the capacity of the linkcapacity of the junctions rather than the capacity of the link. . Guidance on urban road crossGuidance on urban road cross--sections to use can be found by sections to use can be found by referring to: referring to: Road CrossRoad Cross Sections stated for different categories ofSections stated for different categories of roads in roads in gg

local Road local Road Authority Authority Publications.Publications. ‘‘Roads and Traffic in Urban Area’ as published by theRoads and Traffic in Urban Area’ as published by the Stationary Stationary

Office in London.Office in London. TA 79/99 in Volume 5 of the UK DMRB which gives guidance on TA 79/99 in Volume 5 of the UK DMRB which gives guidance on

traffic capacities of Urban Roads. traffic capacities of Urban Roads. TA 44/92 in Volume 5 of the UK DMRB which advises on TA 44/92 in Volume 5 of the UK DMRB which advises on

capacities, queues etc at Road Junctions.capacities, queues etc at Road Junctions.

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