improving road safety with effective road traffic signs
TRANSCRIPT
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