Improving Road Safety with Effective Road Traffic Signs

Improving Road Safety with Effective Road

Traffic Signs

Program

• Current Situation & Trends

• Legal & SANS Overview

• Science of Sign Sheeting Technology

• Key Points & Recommendations

Source: OECD Vulnerable Road User Report

Current Roadway Situation

Increasing• Vehicle population

• Kilometers travelled

• Heavy Truck Traffic

• Vulnerable Road Users (Pedestrians/Cyclists)

• Congestion

• Complexity

1939

Today

Road Safety Situation – Fatality Projection

Source: Elizabeth Kopits and Maureen Cropper

World Bank Region % change 2000 - 2020

South Asia 143.9%

East Asia & Pacific 79.8%

Sub-Saharan Africa 79.8%

Middle East & North Africa

67.5%

Latin America & Caribbean

48.1%

Europe & Central Asia 18.2%

Sub-total 83.3%

High-income countries - 27.8%

Global total 66.4%

Road Safety Situation - Nighttime Accidents & Fatalities

Source: “Road Transport Lighting for Developing Countries,” August 2002 Draft, CIE TC 4-37.

0

5

10

15

20

25

30

35

40

45

50

Per

cent

age

at N

ight

Shanghai 2000 Bangladesh 1998 Zimbabwe 1998 Botswana '94-95 EU 15 - 2000

All Accidents

Fatalities

All Village & Rural Accidents

An effective and reliable communication system providing the safety and guidance

information required for safe movement within the roadway system is a basic

requirement of a Safe Roadway.

Traffic Signs (& Road Markings) are the primary, and often sole,

means of communication between Road System and Road User

Road Safety Situation - Driver Information Needs

Daytime Many landmarks available

Driver task relatively easy

NighttimeFew landmarks remain

Task more difficult

Signs need to be as effective at night as they are during the day

Sometimes this requirement is not always met

Daytime Night time

Legal Reference

• National Road Traffic Act 93 of 1996

(Sections 56 – 59)• Chapter IX of NRTR 2000

–Reg. 285 Purpose & Classification–Reg. 286 Dimensions–Reg. 286A Colours–Reg. 287 Manner of Display

SABS National Standards

• SANS 1519-1:2006 Road Signs Part 1: Retro reflective sheeting material– Class I / Class III / Class IVa & IVb– Reflective / Colour/ Durability performance

• SANS 1519-2:2014 Road Signs Part 2: Performance requirements for road signs– Coatings on finished sign (printing/vinyl/overlay etc.)– Structural requirements– Refers to SANS1519-1 for reflective requirements

• SANS 1555:2011 Roadworks Delineators – SANS 1519-1 Material Reference (Class III minimum)– Flexible signblade performance– Locking mechanism to prevent blade separation from base

.

General Policy and Sign Design Principals are contained in the

Southern African Development Community (SADC) Road Traffic Signs Manual

.

Requirements of a Road Sign or Safety Device

• Fulfill a need• Command attention• Convey a clear, simple message• Command the respect of road users• Allow adequate time for the correct

response from road users

SADC Sign Manual 2012

SADC RTSM Guideline

.

So, how does Reflectivity work?

3 Types of Reflection

Available Retro-Reflective Sheeting Technology for Road Traffic Signs

Sign Sheeting Technology

1940 1970

1985-2015

Beads as Retro-reflectors

Only 28% of spherical bead surface Bends light just right to cause

retroreflection

Truncated Cube Corners Have Limitations

Only 65% of the truncated cube surface is retroreflective

Light entering the corner only reflects twice

Truncated cube corners (200x)

Full Cube Optics

Most Efficient Portion

Full Cube Optics

Still uses mirror reflection

There are no dead corners

100% of full cube surface is retro-reflective

Available Technology - How Light Return Technology has Improved

814

32

58

0

10

20

30

40

50

60

%

Reflective Sheeting Efficiencies

Reflective Sheeting Efficiencies

Enclosed Bead

Encapsulated Bead

Truncated Cube Corner

Full Cube Corner

Coefficient of Retroreflection: RA

Luminance / Illuminance cd / lux / m2

Intensity of a Light Source = Candela cd

Illuminance: Light falling on a unit area lux

Luminance: measured brightness of the reflected light from a surfaceIntensity / unit area cd / m2

Reflectivity - Units of Measurement

Cone of Returned Light

RetroreflectorReflected Light in Divergence Cone

Light Source Direction

Observation Angle

• The angle between the line formed by a headlight beam striking a sign surface and the line formed by the retro-reflected light beam at the driver’s eye

• This angle is usually small (e.g. 0,2 / 0,33 degrees)

Observation Angle

• Observation angle is a critical factor when determining how bright a sign appears

• As the observation angle increases the sign will appear less bright

Entrance Angle

• The angle between the line formed by a light beam striking the sign surface at some point and a line perpendicular to the sign surface at that same point.

Entrance Angle

• The position of the vehicle in relation to the sign will determine the Entrance Angle

• Larger angle (e.g. 5deg/30deg/60deg etc)

Entrance Angle

• The wider the Entrance Angle becomes will reduce the reflective performance (brightness) of the sign

Angularity Factors to Consider

• Where is the vehicle on the roadway• What type of vehicle is it (e.g. truck or car)• What is the position of the reflective sign

in relation to the roadway• Where is the reflective sign in relation to

the vehicle

Factors that Determine Sign BrightnessFactors that Determine Sign Brightness

DRIVERVisual AcuityAgePerception Reaction TimeBlood Alcohol Level

VEHICLEVehicle typeDimensions

Headlamp typesHeadlamp output

Windshield Transmission

ROADWAYCritical Distances GlareSpeed Background Complexity

Surround LuminanceSign Size Roadway AlignmentLegend Complexity Sign PositionSign Criticality Entrance AngleSign Contrast RatioDirt on Sign

Why Brighter Signs are Required

.

• Aging Population

• Growing Truck Fleet

• VOA Headlamps

Signing Considerations & Trends

Older Drivers

• Aging produces a natural decline in sensory, cognitive and motor (physical) functioning

• Studies show that required light need doubles every 13 years after the age of 20

• Studies have determined that easier-to-see-and-read signs can help older drivers retain their freedom of mobility and reduce the likelihood of being involved in traffic accidents

Older Drivers

* Night Lights...lighting the way (Answering Your Questions about Traffic Sign Retroreflectivity), U.S. Department of Transportation, Federal Highway Administration

• Aging Population

• Growing Truck Fleet

• VOA Headlamps

Signing Considerations & Trends

.

Camera 535mmabove

Headlight

Camera 1270mmabove

Headlight

Larger Observation Angle for Trucks

.

Camera 535mmabove

Headlight

Camera 1270mmabove

Headlight

Larger Observation Angle for Trucks

• Aging Population

• Growing Truck Fleet

• VOA Headlamps

Signing Considerations & Trends

Visually Optically Aimiable Headlights

Sign Design PrinciplesThe amount of light available to the traffic sign varies depending on the position of the sign and the vehicle.

14%17 %

22 %100 %

Source: TRB VIS 2005 “Percent Drivers Served” N.Johnson

Sign Viewing Distance-Scenario Basics

Sign becomes visible as

a very small white object

Visual Acquisition Process

Sign becomes visible as

a very small white object

Sign becomes visible as

a very small white object

Minimum Sign Reading Distance

Last Look

Next Avenue

Sign Viewing Distances – 2 Scenarios

• Sign Position (Overhead Freeway)• Letter Size 400mm • Information Sign (3 lines)• 120 km/h (75 mph)• 3 seconds reading time Minimum

Ref: TRB VIS 2005 “Percent Drivers Served” N.Johnson

• Sign Position (Overhead Urban)• Letter Size 200mm• Information Sign (1 line)• 64 km/h (40 mph)• 2.3 seconds reading time minimum

Carlton 50Sandstone 10

Duluth 80Next Avenue

Critical Distance Range: 150 - 50 meters

Critical Distance Range: 71 - 30 meters

Additional Research: “Driver Eye Fixation and Reading Patterns while Using Highway Signs under Dynamic Nighttime Driving Conditions: Effects of Age, Sign Luminance and Environmental Demand” Schieber, Frank; Heimstra Human Factors Lab – University of South Dakota, TRB 2004-001951

Luminance Performance Comparison

Class 4a&b (Full Cube Prismatic)

Class 3 (Truncated Prismatic)

Class 1(Enclosed Lens Bead)

Critical Distance

Class 3Class 1 Class 4

Fluorescent Sheeting Technology

• Refers to the sheeting COLOUR performance• Provides improved daytime colour and low light

performance of signs (e.g. dusk, dawn, misty conditions)

• Fluorescent performance is included in SANS 1519-1

How Fluorescence Works

Short wavelength light is absorbed by sign

Ordinary Colour

Short wavelength light is reemitted as longer wavelength light.

Fluorescent Colour

Fluorescent Retro-reflective signs

• Fluorescent colour increases daytime sign visibility

• 40% earlier detection

• Eye tracking studies have shown additional 2,5 seconds decision and reaction time for drivers travelling at 80 km/h

Source: Sintef, “Visual Performance of Fluorescent Retroreflective Traffic Control Devices,”

Rank Improvement Desc. Benefit/Cost Ratio1 Illumination 22.82 Upgrade Median Barrier 22.63 Traffic Signs 22.44 Relocated/Breakaway Utility Poles 17.75 Remove Obstacles 10.76 New Traffic Signals 8.57 Impact Attenuators 8.08 New Median Barrier 7.69 Upgrade Guardrail 7.510 Upgrade Traffic Signals 7.411 Upgrade Bridge Rail 6.912 Improve Sight Distance 6.113 Median for Traffic Separation 6.114 Groove Pavement for Skid 5.815 Improve Minor Structure 5.316 Turning Lanes and Channelization 4.517 New RR Crossing Gates 3.418 New RR Crossing Flashing Lights 3.119 Pavement Markings and Delineation 3.120 New RR Crossing Lights and Gates 2.9

Cost Benefit Ratio

Source: Table IV-7 Highway safety improvements with the highest benefit-cost ratio

Cost Benefit RatioCategory # projects Av Cost £ Acc Red % % FYRR

Roundabout 18 14769 49 134

Speed limits 6 1117 33 1035

Speed camera 28 18236 13 260

Traffic Calming 14 46093 57 216

Warning Signs 36 553 46 3491

Road Markings 63 2537 41 820

Traffic Signals 15 40717 67 157

Source: Royal Society for Prevention of Accidents (UK)

Cost Effective Signs

• Components of a Road Traffic Sign– Reflective Sheeting – Sign Backing– Sign Manufacture Labour costs – Sign Post– Sign Installation costs

Key Points to Remember

• A developed roadway infrastructure is needed for road safety -- Effective Traffic Signs are a key part of this!

• High brightness signs (day and night) are used to improve roadway safety – They are cost effective!

• The distances at which higher brightness is provided is important – Critical Distance

• Truck Drivers and Older Drivers need signs which provide more brightness (especially at high observation angles)

• Daytime brightness of signs may be increased through the use of fluorescent reflective sheeting.

• Nighttime brightness of signs may be increased through the use of more efficient sheeting technology.

In 2015, should South Africa rely on technology from the 1940’s to Guide and Warn

Motorists.....?

What could possibly go wrong.......!!

Recommendations• Provide regular educational training programs to outline current

requirements, available technology & recommendations for effective & compliant Road Traffic Signs / related products

• Review the current retro-reflective sheeting recommendations contained in Table 1.1 of SADC Sign Manual and amend to the Table to include latest sheeting technology

• Road Traffic Sign Manufacturing & Installation procedures need to be measured according to credible and implementable SABS standards

• SANS documents should be referenced and regulated in Road Traffic Sign contract & tender documents as the minimum qualification for tendering.

• Revise the SADC RTSM & South African Road Traffic Regulations to include the latest SABS standards references

Thank You