Traffic Safety Strategies
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TDM Encyclopedia
Victoria Transport Policy
Institute
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Updated
March 8, 2007
This chapter describes strategies for improving traffic safety and public health, particularly mobility management strategies. For more information on Mobility Management safety impacts see Litman and Fitzroy, 2005.
Introduction
Traffic crashes cause deaths, injuries, pain, disabilities, lost productivity, grief, material damage, and transportation decisions can affect personal safety (risk of being attacked) and aerobic fitness. Changes in travel patterns affect traffic risk and public health in many ways, as summarized below (Safety Impacts of TDM).
· Strategies that reduce traffic speeds can significantly reduce per-mile crash frequency and severity where they are applied, and encourage reductions in total vehicle travel.
· Strategies that reduce traffic congestion tend to reduce the frequency of crashes but can increase the severity of those crashes that do occur. Strategies that shift automobile travel time, route or destination but do not reduce total vehicle travel probably do little to increase road safety or public health, and may increase injuries and fatalities.
· Strategies that shift travel from driving to transit and ridesharing tend to provide medium to large road safety benefits.
· Strategies that shift automobile travel to nonmotorized modes may increase risk per mile for the people who change mode, but this can be offset by reduced risk to other road users, reduced trip length, and Health benefits from aerobic exercise.
· TDM strategies that reduce total personal travel can provide large safety benefits. Each 1% reduction in reduced motor vehicle travel typically reduces total crashes and casualties by 1.4% to 1.8%.
· Strategies that create more Accessible land use patterns and more balanced transportation systems can provide large reductions in per capita crash costs and increase aerobic health.
· Some TDM strategies improve personal security or promote cycle safety.
Some transportation improvement projects can have unanticipated negative safety impacts. Elvik (2001) points out that, although highway capacity expansion is often justified based on projected crash reductions, such projects must fulfill certain criteria in order to really improve road safety. “First of all, the new road must not lead to increased speed, which entails more stringent speed regulation. The new road must not encourage more traffic, which also means more accidents.”
Strategies That Improve Traffic Safety
The figure below illustrates the relationships among various traffic safety strategies. The two major categories are Engineering, which involves safer vehicles and roadways, and Behavior Changes, which include mobility management (changes in travel mode, route, destination, frequency and speed), more cautious driving, and actions by vehicle occupants such as using seat belts, child restraints and helmets.
Figure 1 Traffic Safety Strategies
This figure illustrates the relationships among various traffic safety strategies.
Wilson and Lipinski (2004) describe many of the engineering strategies for improving traffic safety. TDM strategies that tend to improve traffic safety are described below (also see IDOT, 2002).
Traffic Speed Reductions
Strategies that reduce traffic speeds can prevent many collisions, and reduce the severity of damages and injuries that result when crashes occur. Such strategies can provide significant traffic safety benefits, particularly on urban streets. However, some of these benefits may be offset if speed reductions in one area cause traffic to shift to other areas.
For information on traffic speed management programs see:
· U.S. Federal Highway
Administration Speed Management Information (http://safety.fhwa.dot.gov/programs/speedmgnt.htm).
· U.S. National Highway
Traffic Safety Administration Speed Management Information (www.nhtsa.dot.gov/people/injury/speed_management/index.html).
· U.S. Federal Motor Carrier
Safety Administration (www.fmcsa.dot.gov).
TDM Strategies
Traffic Calming, Street Reclaiming, Access Management, Vehicle Use Restrictions.
Optimal Street Widths
Wider
traffic lanes provide give vehicles more room to avoid collisions, but they
increase traffic speeds, which increases crash risk and severity. Annual crash
rates per vehicle-mile tend to be lowest for relatively narrow (about 10-foot)
lane widths, and are highest on wider, lower volume, straight streets with
higher traffic speeds (Swift, 1998; Zegeer, et al, 1994; CTRE, 2006). Urban
streets with 24-foot curb-to-curb widths appear to have the lowest accident
rates.
TDM Strategies
New Urbanism, Traffic Calming,
Road Space Reallocation
Mobility Substitutes
Mobility substitutes include telecommunications and delivery services that substitute for physical travel and reduce vehicle trips. This tends to increase safety, although in many cases there are Rebound Effects, such as the tendency of telecommuters to make special trips for errands that they would otherwise perform while commuting, and to move farther from their worksite.
TDM Strategies
Telework, Freight
Transport Management
Land Use and Transportation System Changes
Land use patterns affect per capita automobile travel (Land Use Impacts on Transportation). Automobile-oriented land use patterns tend to increase per capita automobile travel, which tend to increase traffic crashes and causalities.
Automobile-oriented transportation systems are also associated with reduced exercise, while strategies that increase walking and cycling can provide significant health benefits (Frank and Engelke, 2000). Many of the Active Community Environment factors advocated by the U.S. Center for Disease Control, such more walkable communities and incentives for reduced automobile travel, are supported by TDM (Killingsworth and Lamming, 2001).
TDM Strategies
Smart Growth, Location Efficient Development, New Urbanism, Transit Oriented Development, Access Management, Traffic Calming, Vehicle Restrictions, Carfree Planning, Least Cost Planning, Institutional Reforms.
Mode Shifting
TDM strategies that shift travel mode can have a variety of safety and health impacts.
Transit
Shifting from driving to public transit tends to reduce crash risk per passenger trip because professional drivers tend to have lower crash rates, bus occupants are safer than automobile occupants, and because it reduces total vehicle traffic (Litman, 2004).
TDM Strategies:
Transit Improvements, Shuttle Services, HOV Priority, Park & Ride, Bike/Transit Integration, Transit Oriented Development
Ridesharing
Ridesharing tends to reduce overall crash risk by reducing total vehicle traffic. For example, two people who carpool rather than drive alone bear about the same level of internal risk (assuming that their driving skills and vehicles are equally safe), but reduce risk to others by using one vehicle rather than two.
TDM Strategies
Ridesharing, HOV Priority, Park & Ride
Nonmotorized Transport
Shifting from driving to nonmotorized travel (walking and cycling) tends to have mixed safety impacts. Nonmotorized travel tends to have relatively high per-mile crash rates, but nonmotorized travel imposes minimal risk to other road users, and non-motorized trips are often significantly shorter than automobile trips they replace (for example, a consumer may choose between walking to a local store or driving to a more distant supermarket). Experienced adult cyclists tend to have much lower per-mile crash rates than young, inexperienced cyclists. In addition, nonmotorized travel provides health benefits that offset crash risk.
A number of targeted strategies and programs can reduce
crash risk to nonmotorized travelers (Pucher and Dijkstra, 2000; Retting,
· Pedestrian and cycling classes can be integrated with Commute Trip Reduction and School Transport Management programs, personal safety and fitness, and physical education programs.
· Adult cycling skills classes can be taught at recreational facilities, or provided through local traffic safety associations.
· Public education campaigns targeting motorists, cyclists, and pedestrians covering cyclists and pedestrians rights and safety skills.
Although many communities have some programs, few communities have enough pedestrian and cycling programs to educate a significant portion of the population. Responsibility for such programs is fragmented, and there is seldom stable funding.
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Nonmotorized Transport Safety Resources Khaled Abbas, Ibrahim Mabrouk, and Khaled El-Araby,
“School Children as Pedestrians in Marvin Aoki and Lawrence Children on the Move (www.ecoplan.org/children) provides information on children’s transportation issues. Kerbcraft; Smart Strategies for Pedestrian Safety, UK Department of Environment, Transport and the Regions (www.roads.detr.gov.uk/roadsafety/rs2/kerb.pdf), 1998. A curriculum for teaching children how to cross streets where there is no traffic signal. Charles Komanoff, Killed by Automobile, Right of Way (www.rightofway.org), 1999. League of American Bicyclists Education Programs (www.bikeleague.org/ec2/education.htm) provides a variety of resources. NHTSA, Pedestrian Safety Toolkit, National Highway Traffic Safety Administration (www.nhtsa.gov), 1999. Perils for Pedestrians (www.pedestrian.org) is a cable television series promoting awareness of issues affecting pedestrian safety. Their website includes advocacy tips and links to other pedestrian organizations. Problems of Attention and Visual Search in the Context of Child Pedestrian, Behaviour, UK DETR, (www.roads.detr.gov.uk/roadsafety/rscdr/no8/index.htm), 1999. Pedestrian/Bicyclist Resource Kit, FHWA (www.ota.fhwa.dot.gov/walk). Pedestrian and Bicycle Crash Analysis Tool, FHWA-RD-99-192, FHWA (202-493-3315; www.tfhrc.gov). Richard
A. Retting, Susan A. Ferguson and Anne T. McCartt, “A Review of
Evidence-Based Traffic Engineering Measures Designed to Reduce
Pedestrian-Motor Vehicle Crashes,” American Journal of Public Health,
Vol. 93, No. 9 (www.ajph.org), Sept. 2003,
pp. 1456-1463. R.A. Schieber and N.J. Thompson, “Developmental risk factors for childhood pedestrian injuries” Injury Prevention, Vol. 2, 1996, pp. 228-236. Speed Kills, The Benefits of Slower Speeds, and Why Reduce Speeds, UK Anti-speed Campaign (www.speed-campaign-info.fsnet.co.uk). Study Addresses Safety Of Children On Their Way To And From School, CUTR, (www.cutr.eng.usf.edu/new/news_let/articles/winterB98/winterB98-1.htm), 1998. |
TDM Strategies
Pedestrian and Cycling Improvements, Pedestrian and Cycling Encouragement, Universal Design, Bike/Transit Integration, Traffic Calming, TDM Marketing
Vehicle Mileage Reductions
Reduced per capita mileage tends to reduce per capita crash rates. All else being equal, each 1% reduction in a vehicle’s mileage should reduce its chances of having a crash by 1%, and also reduce crash risk to other road users. Since about 70% of crashes involve multiple vehicles, each 1.0% mileage reduction should reduce total crash costs by 1.7% if other factors are constant. The empirical evidence also indicates that broad reductions in driving reduce overall crash rates.
TDM Strategies
Commute Trip Reduction, Distance-Based Charges, Parking Pricing, Road Pricing, Telework, Freight Transport Management, Vehicle Restrictions and various other TDM strategies.
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Congestion Pricing Safety
Impacts ( The
central · Total vehicle–kilometres reduced by 12%, car traffic reduced by 30%, crashes declined 28%. · Moped and motorbike travel increased 10 –15%, with 4% fewer crashes. · Bicycle travel increased 20%, with a 7% reduction in crashes. · Crashes involving pedestrians declined 6%. · Increased bus journey time reliability by up to 60%. · No evidence of any overall increase in road traffic outside the zone. · Subjective improvements in noise and air quality. |
Pay-As-You-Drive Vehicle Insurance
Pay-As-You-Drive converts vehicle insurance premiums from a fixed cost into a variable cost. It incorporates all existing rating factors so lower-risk motorists pay less per mile than higher-risk motorists. This price structure gives higher-risk motorists a greater incentive to reduce their driving than lower-risk motorists. For example, a motorist who currently pays annual premiums of $375 would pay 3¢ per mile, and is likely to reduce mileage by about 6%. A higher-risk motorist who currently pays annual premiums of $1,250 would pay 10¢ per mile, and so could be expected to reduce mileage by about 18%. To the degree that insurance companies can accurately identify motorists who are higher risk per mile, this should provide an additional reduction in crash rates. As a result, Pay-As-You-Drive Insurance is predicted to reduce mileage an average of 10% among participants, while crash costs and fatalities decline 15% or more.
TDM Strategies
Pay-As-You-Drive Vehicle Insurance, Distance-Based Charges
Improved Traffic Law Enforcement
Various traffic law enforcement strategies can increase compliance with safety-related traffic laws, including increased observance of speeds, yielding and traffic controls (Blakey, 2003). New technologies allow fleet operators and parents to monitor driving patterns and identify those that are relatively risky (www.drivediagnostics.com).
Graduated Licenses
Williams (2003) describes graduated drivers license policies, which place various restrictions on younger drivers, such as prohibitions on driving late at night or with multiple passengers. Crash reductions of 20-30% are reported from these programs.
Other Strategies
Elvik (2003) identifies many traffic safety strategies that he calculates can be cost effective when all benefits are considered. He predicts that current safety strategies will reduce crash fatalities 10-15%, but that 50-60% fatality reductions are possible if all cost-effective safety strategies were implemented.
Strategies With Mixed Safety Impacts
Travel Time and Route Shifts
TDM strategies that shift vehicle travel from peak to off-peak periods or from congested highways to alternative routes have mixed safety impacts. Shifting vehicle trips to less congested roadway conditions can reduce crashes, but the crashes do occur tend to be more severe due to higher travel speeds. As a result, the road safety impacts of TDM strategies that shift travel times and routes can vary, depending on specific circumstances, and are difficult to predict.
Many strategy’s safety impacts depend on how and under what circumstances they are implemented. For example, Road Pricing, Vehicle Restrictions and Carfree Planning that are applied on just some roads or during certain times may simply shift automobile travel times and routes, providing little safety benefit, but if implemented with other complementary TDM strategies that improve transportation alternatives and provide incentives to reduce overall automobile travel, there may be significant safety benefits.
TDM Strategies
Flextime, Congestion Pricing, Parking Pricing, Vehicle Restrictions, Carfree Planning.
Access Management
Access Management is a set of roadway design principles intended to increase traffic efficiency by reducing the number of driveways and intersections on major roads, and clustering development. This tends to reduce per-mile crash rates, improve walking and cycling conditions, and encourage transit and ridesharing. If it increases vehicle traffic volumes and speeds, it may increase total crashes and crash severity. If it supports more efficient land use and mode shifting, it can reduce total road risk.
Demosthenes (2003) finds that urban arterial crash rates are determined largely by the frequency and design of access points that serve land development and local streets. Access locations account for more than 60% of vehicular crashes in urban areas. He estimates that incorporating access management strategies when considering local street plans and development site plans can significantly reduce crash rates, as well as providing mobility and community livability benefits. Failing to limit access points and creating community or regional plans results in more frequent intersections, the need for many traffic signals and frequent driveways, establishes an almost permanent high-level crash rate that will plague the community for decades. He calculates that modern access management strategies can prevent more than 1,500 crashes in a 3-mile corridor in a five-year period.
TDM Strategies:
Strategies that Improve Personal Security
Some TDM strategies affect people’s exposure to personal security threats. Several TDM strategies can help increase personal security. As more responsible citizens walk, cycle and use transit, their presence in the street and other public areas tends to reduce the overall risk of personal assault in an area. Some TDM strategies address these security risks directly, and land use management strategies increase community cohesion and “eyes on the street” are likely to increase personal security. Strategies that increase Transportation System Resilience can help reduce a broad range of risks to individuals and communities.
TDM Strategies
Address Security Concerns, Guaranteed Ride Home, Street Reclaiming, Pedestrian and Bicycle Improvements, Transit Oriented Development, New Urbanism, Transportation Resilience.
Strategies that Improve Public Health
Some analysis indicates that the potential Health and Fitness benefits from policies and programs that increase active transportation (walking and cycling) may be even greater than potential benefits from crash reductions. More than ten times as many people are disabled and die from cardiovascular diseases as from traffic crashes, so even a small improvement in aerobic fitness can provide large public health benefits. Many TDM strategies support and encourage nonmotorized transportation, either directly or by creating more Livable communities where walking and cycling is feasible. Universal Design can be particularly important for improving active transportation opportunities for people with disabilities.
TDM Strategies
Bicycle and Pedestrian Encouragement, Traffic Calming, Universal Design, School Transport Management, Address Security Concerns, Street Reclaiming, Pedestrian and Bicycle Improvements, Smart Growth, New Urbanism, .
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When
I die I want to go like my grandfather – in his sleep. Not screaming like the
other passengers in his car. |
References And Resources For More Information
Leslie T. Blakey (2003), “Red-Light Cameras: Effective Enforcement Measure for Intersection Safety,” ITE Journal, Vol. 73, No. 3, Institute of Transportation Engineers (www.ite.org), March 2003, pp. 34-43.
BTS (2000), Transportation Safety Data, Bureau of Transportation Statistics, USDOT (www.bts.gov/programs/btsprod/nts/chp3v.html).
CTRE (2006), Four-Lane to Three-Lane Conversion: Research Projects/Reports, Center for Transportation Research and Education (www.ctre.iastate.edu); available at www.ctre.iastate.edu/research/4laneto3lane.htm.
Philip Demosthenes
(2003), How Planning
Decisions Impact Highway Collision Histories, 2nd Urban Street Symposium,
P. Elsenaar and S. Abouraad (2005), Road Safety Best Practices - Examples and Recommendations, Global Road Safety Partnership (www.grsproadsafety.org); available at www.grsproadsafety.org/themes/default/pdfs/Road%20Safety%20Best%20Practices.pdf. This manual describes specific measures for reducing roadway risk, particularly in developing counties. It covers: Campaign and Enforcement, Awareness and Partnership, Crash Databases, Treatment of Black Spots, Road Design and Speed Management, Heath and Road Safety, and Prehospital Care.
Rune Elvik (2001), “Zero Killed in Traffic – from Vision to Implementation,” Nordic Road & Transport Research, No. 1 (www.vti.se/nordic/1-01mapp/toi1.htm), 2001.
Rune Elvik (2003), “How Would Setting Policy Priorities According to Cost-Benefit Analyses Affect the Provision of Road Safety,” Accident Analysis & Prevention, Vol. 35 (www.elsevier.com/locate/aap), pp. 557-570.
Insurance Institute for Highway Safety (www.carsafety.org).
International Traffic Medicine Association (www.iaatm.org) works to reduce human harm from traffic crashes by improving crash prevention, injury prevention, emergency response and injury treatment.
International Cooperation on Theories and Concepts in Traffic Safety (www.ictct.org) is an association that works to achieve a deeper understanding of traffic risk and opportunities for accident prevention.
IDOT, SMS Toolbox of Highway Safety Strategies, Iowa Department of Transportation (www.iowasms.org/toolbox.htm) is a compilation of highway crash data and potential safety improvement strategies.
Richard E. Killingsworth and Jean Lamming (2001),
“Development and Public Health; Could Our Development Patterns be Affecting Our Personal Health?” Urban
Land, Urban Land Institute (www.uli.org),
July 2001, pp. 12-17
Charlie Komanoff (1999), Killed by Automobile, Right of Way (www.rightofway.org).
W.A. Leaf and D.F. Preusser (1998), Literature Review on Vehicle Travel Speeds and Pedestrian Injuries, National Highway Traffic Safety Administration, USDOT (www.nhtsa.gov); available at www.nhtsa.gov/people/injury/research/pub/hs809012.html.
Todd Litman (2001), Transportation Cost and Benefit Analysis: Techniques, Estimates and Implications, Victoria Transport Policy Institute (www.vtpi.org); includes a chapter on “Crashes, Security and Health Impacts” at www.vtpi.org/tca/tca0503.pdf.
Todd Litman (2006), Evaluating Public Transit Benefits and Costs, VTPI (www.vtpi.org), 2004; available at www.vtpi.org/tranben.pdf.
Todd Litman and Steve Fitzroy (2005), Safe Travels: Evaluating Mobility Management Traffic Safety Impacts, VTPI (www.vtpi.org); available at www.vtpi.org/safetrav.pdf.
Frank Markowitz, Stanley Sciortino, Jack Lucero Fleck and Bond M. Lee (2006), “Pedestrian Countdown Signals: Experience With An Extensive Pilot Installation,” ITE Journal, Vol. 76, No. 1 (www.ite.org), January 2006, pp. 43-48.
Ted Miller (1991), The Costs of Highway Crashes, FHWA (
National Highway Traffic Safety Administration (www.nhtsa.dot.gov) provides comprehensive traffic crash data and information on safety programs.
Robert Noland (2001), Traffic Fatalities And
Injuries: Are Reductions The Result Of ‘Improvements’ In Highway Design
Standards?,
OECD (2001), International Road Traffic and Accident Database, Organization for Economic Cooperation and Development (www.oecd.org); available at www.bast.de/htdocs/fachthemen/irtad//english/we2.html.
Ottawa (2004), Area Traffic Management Guidelines; Appendices (Draft), Department of Public Works and Services City of Ottawa (www.ottawa.ca); available at http://ottawa.ca/calendar/ottawa/citycouncil/trc/2004/10-20/ACS2004-TUP-TRF-0012%20Annex%202.pdf and http://ottawa.ca/calendar/ottawa/citycouncil/trc/2004/10-20/ACS2004-TUP-TRF-0012%20Appendix%20A-H.pdf.
John Pucher and Lewis Dijkstra (2000), “Making
Walking and Cycling Safer: Lessons from
Richard A. Retting, Susan A. Ferguson and Anne T. McCartt (2003), “A Review of Evidence-Based Traffic Engineering Measures Designed to Reduce Pedestrian-Motor Vehicle Crashes,” American Journal of Public Health, Vol. 93, No. 9 (www.ajph.org), Sept. 2003, pp. 1456-1463.
Road Safety Audit Website (www.roadwaysafetyaudits.org) provides access to resources related to safety audits.
Road Safety Cafe (www.roadsafetycafe.co.za) provides a variety of road safety information.
Royal Society of the Prevention of Accidents Website (www.rospa.org.uk) provides accident statistics and safety information.
Safety Conscious Planning (www.fhwa.dot.gov/planning/SCP), is a U.S. Federal Highway Administration website providing information on ways to incorporate traffic safety into transportation planning.
Jack Stuster and Zail Coffman (1998), Synthesis of Safety Research Related to Speed and Speed Limits, Federal Highway Administration, FHWA-RD-98-154 (www.tfhrc.gov/safety/speed/speed.htm).
Peter Swift (1998), Residential Street Typology and Injury Accident Frequency, Swift and Associates (www.sierraclub.org/sprawl/transportation/narrow.asp).
TC (annual reports), Canadian Motor Vehicle
Traffic Collision Statistics, Transport
Jing-Shiarn Wang, Ronald R. Knipling and Lawrence J. Blincoe (1999), “The Dimensions of Motor Vehicle Crash Risk, Journal of Transportation and Statistics, Vol. 2, No. 1, May 1999, pp. 19-43.
WHO
(2000), Carlos Dora and
Margaret Phillips (eds), Transport, Environment and Health, World Health Organization
Regional Publication, European Series, No. 89 (www.euro.who.int/document/e72015.pdf).
WHO (2004), World Report on Road Traffic Injury Prevention: Special Report for World Health Day on Road Safety, World Health Organization (www.who.int); available at www.who.int/world-health-day/2004/en.
Allan F.
Williams (2003),
“Graduated Licensing in the
Eugene M. Wilson and Martin E. Lipinski (2004), Road
Safety Audits: A Synthesis of Highway Practice, National Cooperative
Highway Research Program (NCHRP) Synthesis 336: Road Safety Audits (http://trb.org/publications/nchrp/nchrp_syn_336.pdf).
Charles
V. Zegeer, Richard Stewart, Forrest Council and Timothy R. Neuman (1994),
“Accident Relationships of Roadway Width on Low-Volume Roads,” Transportation
Research Record 1445, TRB (www.trb.org), pp. 160.
Zegeer, et al (2001), Identification of Severe Crash Factors and Countermeasures in North Carolina, North Carolina Department of Transportation (www.ncdot.org).
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Encyclopedia is produced by the Victoria Transport Policy Institute to help
improve understanding of Transportation Demand Management. It is an ongoing
project. Please send us your comments and suggestions for improvement.
Victoria Transport Policy Institute
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Phone & Fax 250-360-1560
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