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Development of a Bicycle Safety Prediction Methodology

Research Problem Statement
More than 4,400 pedestrians and 700 cyclist fatalities occurred 2008, and over 100,000 non-motorized injury crashes were reported. Combined, non-motorized fatalities represent nearly 14% of all traffic fatalities in the United States. Moreover, many pedestrian and bicycle crashes go unreported, particularly crashes that don’t result in serious injuries and crashes that occur between users on multiuse pathways.
Significant research has gone into the development of safety prediction and mitigation methods for vehicles, but comparatively little has been completed for bicycles and pedestrians. Non-motorized travel and interest in promoting it are both on the rise, however. The number of non-motorized trips has increased by 25 percent since 2001 according to the National Household Travel Survey, and nearly 12 percent of all trips are now made by biking or walking. Moreover, improved awareness of the congestion and health benefits of active transportation mean that transportation agencies are focusing more resources on improving bicycle and pedestrian facilities and overall safety. Targeted research on non-motorized safety prediction is needed to ensure that these investments result in the intended safety benefits.
The recently completed AASHTO Highway Safety Manual (HSM) establishes a methodology for estimating the potential change in crash frequency or severity due to the installation of a particular engineering treatment at intersections and on roadways. The HSM used previous research to develop “Crash Modification Factors” (CMFs) that relate specific interventions (e.g., protected left-turn phasing) to their expected effectiveness in reducing crashes. While the HSM provides numerous CMFs for automobiles, few treatment had sufficient research to include pedestrian and/or bicycle CMFs. For instance, Chapter 14 of the HSM provides only 5 intersection CMFs for pedestrian treatments and 1 for cyclists, whereas numerous treatments are listed in the “trends” section of the chapter as having insufficient data to develop a CMF.
Literature Summary
A number of cities in the United States (e.g. New York City, Portland, Washington, DC) have recently installed innovative bicycle and pedestrian treatments at intersections and on roadways with the intent to improve safety. For instance, leading pedestrian intervals, colored bicycle lanes through intersections, bicycle-specific signals and signal phases, and advanced stop lines are being introduced in several cities to reduce non-motorized user conflicts and crashes.
While several of these treatments have been employed and studied in Western European countries, little research currently exists on the effectiveness of these facilities in the United States. Research on the use and effectiveness of these techniques in the United States is inconsistent and scattered, and should be actively pursued to determine whether and to what extent these treatments benefit bicyclists.
Research Objective
The proposed research will develop a predictive method for geometric treatments at intersections and on roadways for pedestrian and bicycle facilities. To accomplish this, the research must:
1)      identify typical design treatments for pedestrians and bicyclists at intersections and on roadways;
2)      identify prevalent pedestrian and bicycle crash types at intersections and on roadways;
3)      isolate the effect of specific pedestrian and bicycle treatments for the various crash types identified;
4)      identify and/or develop trends for the specific pedestrian and bicycle treatments identified;
5)      codify guidelines and applications for estimating the potential change in crashes due to the installation of specific pedestrian and bicycle treatments that are useful for designers; and,
6)      identify additional research needs.
The investigation should consider signalized and unsignalized intersections and include roads with and without pedestrian and bicycles facilities. Design tools to investigate include, but are not limited to:
  • marking or dashing bike lane or bike travel path through intersections,
  • colored pavement for bike travel paths through intersections,
  • location of stop bars for motor vehicles and bicycles,
  • use of bike boxes at intersections,
  • alternative methods to accommodate bicycle left-turns
  • bicycle signal-heads with accompanying bicycle-specific signal phasing,
  • other pavement markings, signs, and signal designs.
A key outcome of the research would be guidance that could supplement or update the HSM or the pending AASHTO Guide for the Development of Bicycle Facilities. This research could serve to populate the CMF catalogue and supplement the data available in the HSM for bikers and walkers.
Recommended Funding:
Research Period:
            18 months

Urgency, Payoff Potential, and Implementation
 This research has high priority. In addition to providing guidance to practitioners on treatments for bicycle and pedestrian facilities, this research would provide additional measures for determining the safety benefits or drawbacks for various treatments.
Jurisdictions throughout the country are searching for quantifiable solutions for bicycle and pedestrian safety issues at intersections and along roadways.
State DOTs, local governments, traffic engineers, roadway designers, traffic operations and maintenance personnel, pavement markings designers, bicycle and pedestrian facility planners.

This research would influence geometric designs of pedestrian and bicycle facilities on new roadways, reconstruction projects, and resurfacings related to the design of urban roadways and intersections.

Sponsoring Committee:AKD10, Performance Effects on Geometric Design
Source Info:Brian Ray, Kittelson & Associates, Chair of TRB Committee on Geometric Design (AFB10)
Date Posted:09/15/2010
Date Modified:09/15/2010
Index Terms:Bicycle travel, Cyclists, Highway safety, Intersections, Fatalities, Traffic accidents, Nonmotorized transportation, Bicycle safety, Bicycle lanes,
Cosponsoring Committees: 
Pedestrians and Bicyclists
Safety and Human Factors

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