Table of Contents

 

Source/Location	Bicycle-Involved Collisions per Million Bicycle Miles
Kaplan1	113
Moritz2	66
Expressways in Santa Clara County	19+ reported
Bridges/Tunnels Studied from Chapter 5	16 reported
Internet Survey	24
SR 101, Humbolt County, CA, District 1	5 reported

 

Collision Patterns

The specific circumstances involved in each collision are also important to studying bicycle collisions. Observing large groups of collisions may make it possible to develop trends and thereby identify ways to improve safety. A study of bicycle-related collisions on freeways in Caltrans Districts 1, 2, and 3 provided the following results.

A total of 41 collisions occurred on the freeway in the nine years of study (1990-1998). Bicycle-motor vehicle collisions accounted for 61 percent of all collisions in the study. The bicyclist was found to be at fault by the reporting police officer in 73.2 percent of the collisions. The two most prevalent causes of bicycle-motor vehicle collisions were improper turns (29.3 percent) and the influence of alcohol (19.5 percent). A high percentage of collisions involved injury (85.4 percent); 7.3 percent of reported collisions were fatal. There was a fairly even distribution of collisions that occurred on freeways that allowed bicycle access (61 percent) versus freeways where bicycle access was restricted (39 percent). The table below lists some bicycle-on-freeway collision patterns.

Internet Survey

During the course of this study, Caltrans conducted a survey of bicyclists over the Internet. Several questions tailored specifically to this study were added to the survey. Some collision rates were derived from the data, and information was compiled regarding the percent of injury collisions, percent involved with motor vehicles, and percent reported to law enforcement agencies. The table below presents some results from the 1,239 usable surveys. The respondents individually classified their position as to highway or nonhighway.

Bridges and Tunnels

To address questions of the safety record of bicycles on bridges, the collision history of some structures was studied. A collision ratio was established by dividing the number of collisions reported on all structures over a nine-year period by the total length of structures. Two similar ratios were derived for the approaches to the structures. One was for 500 feet on either side of the structure, and the other was for 5 miles. The 5-mile approach was used only for bridges and tunnels under Caltrans jurisdiction. The collision ratio for all structures was 0.62 collisions per mile during the 9-year period. The 500-foot-approach collision ratio was 2.6 collisions per mile. For Caltrans bridges and tunnels only, the collision ratio was 0.84 collisions per mile. The 5-mile approaches had a collision ratio of 1.06.

Although the data includes very few collisions, it shows that bicycle collisions on bridges and tunnels are rare events. This can be due to a number of reasons, but the data compiled here do not indicate that bridges and tunnels currently open to bicycles have more frequent collisions than the adjacent highways.

Statistical Analysis of Collisions and Bicycle Status

In a statistical analysis of all collisions on freeways, the independent variable of Bicycle Status (bicycles permitted or prohibited) was used to attempt to predict collision rates on freeways. Bicycle Status was not found to be an adequate predictor of collision history to the 5 percent level. The lack of Bicycle Status as a significant variable suggests that allowing bicycles on freeways does not have an adverse effect on vehicle collision rates.

Richmond-San Rafael Bridge

Under the current configuration, the Richmond-San Rafael Bridge is not suited for bicycle access, but with minor alterations, bicycles might be able to travel on the shoulder safely. The following is provided as an example of what would need to be done if the bridge were opened to bicycles.

Railing requirements for the Richmond-San Rafael Bridge may be given special consideration due to their width and their location relative to the traveled way. Only slight modifications to the railings, if any, would be needed to make the bridge ready for bicycle travel. Expansion joints would have to be covered to prevent bicycle wheel entrapment.

The Richmond-San Rafael Bridge fits the 8-foot shoulder requirement. Currently, the bridge has 12-foot shoulders over most of the span. The wide shoulders enable bicycles to travel well separated from both motor vehicles and the bridge rail. The 12-foot space does create a problem, in that motor vehicles have been observed using the shoulders for travel and passing. One permanent section has a narrow shoulder, and due to the upcoming seismic retrofit construction, there will be some semipermanent obstructions to the shoulder. Bicycle access should not be granted while there are sections of the shoulder closed to travel and until a continuous 8-foot shoulder can be maintained.

Despite these barriers, the bridge is suited to bicycles in that bicycles could access the bridge without crossing freeway ramps. Direct connections to avoid ramp crossings by bicycles would have to be added.

Recommendations

The recommendations developed by this study include user education, data collection, age restrictions, shoulder geometry, and procedures to allow bicyclists to cross ramps. Key recommendations are offered here in bold face type. Additional information on the recommendations can be found in Chapter 7 of this report.

Pedestrians on Freeways

How to impose pedestrian safety on freeways poses a dilemma. For the 35 percent of pedestrians involved in collisions that entered the freeway illegally, the collision-prevention solution is to stop them from entering. However, the majority of pedestrians involved left their vehicles and may not have been acting illegally. The problem is simply that a pedestrian in or near the right-of-way is in jeopardy.

The solution then is to continue and enhance efforts to inform drivers that they should avoid exiting their vehicles on freeways. When a pedestrian absolutely must leave a vehicle, it is imperative that the pedestrian move as far from the traveled way as possible. Many accidents have been caused when pedestrians installing chains in snowy conditions were struck by motor vehicles. Drivers need to be informed of these dangers.

Data Collection--Count Bicycles

Caltrans currently has no program to count bicycles on freeways. Bicycle travel is difficult to measure and quantify. There is no question that average daily bicycle traffic on freeways is low relative to motor vehicles. A bicycle-counting program needs to be implemented in order to further study bicycles in a quantitative manner. A count program would not need to be comprehensive, in that not all state highways would need bicycle counts. Locations of counts could be established where there appears to be some concentration of bicycle travel, where bicycle collisions have been identified, or where there is public demand.

Rider Requirements

Many freeway sections in California are currently open to bicycle travel, and it is assumed that bicyclists riding these roadways are of a certain level of maturity. Rather than use age, which would be hard to enforce, the possession of a driver's license should be a requirement for using a bicycle on freeway shoulders. Doing so would theoretically meet the following criteria: The user is at least 16 years of age and has a basic understanding of the movements of motor vehicles using freeways .

Because of the higher-than-ordinary severity rate for collisions involving bicycles on freeways, cyclists should be required to wear helmets while riding on freeway shoulders. A vehicle code change would be necessary to implement these recommendations.

Shoulder Width

With the current trend of adding rumble strips to freeway shoulders, the width of freeway shoulders is a concern if bicycles are to be allowed there. Because of wind forces and geometric space requirements, bicycles should not be expected to ride in or directly alongside the traveled way. Therefore, if bicyclists are to be given access to freeway shoulders, they should ride on the shoulder, to the right of the rumble strip.

The width from the edge of the traveled way to the outside of the rumble strips is up to 3 feet. A remaining width of 5 feet provides an area that is comfortable and safe for a bicycle. This gives a total shoulder width of 8 feet, as a minimum, that should be provided on freeways open to bicycles. It was found from the literature search that at 70 miles per hour, a large vehicle can produce enough lateral wind force to overturn a bicycle. Allowing full 8-foot shoulders diminishes the problem of wind pushing the bicyclist. No new freeway segments should be open to bicycles unless there is an 8-foot continuous shoulder. Existing freeways open to bicycles should be improved to provide the continuous shoulder as part of the long-range state highway improvement program.

Drain inlets, which may trap a bicycle tire, must be reconstructed or removed from highway shoulders where bicycles are allowed to ride.

Ramp Crossing

The responsibility of crossing a freeway ramp safely should rest with the bicyclist. Because bicycles are physically smaller than cars and provide less protection, bicyclists are at a major disadvantage in a collision with a motor vehicle. Reasonable expectations are the following:

Cyclists understand they must cross high-speed motor vehicle traffic

Motorists are expecting to merge and diverge smoothly without crossing conflicts.

All freeway ramps at which bicycles are allowed to cross on the freeway side need to be reviewed by Caltrans. While the quantitative recommendations here are based on estimates and not statistically verified by experience, they serve as a starting point for future study and refinement.

A safe crossing sight distance at least equal to the distances cited in Chapter 4 would need to be available to the bicyclist at the location where the ramp would normally be crossed. On freeway off-ramps where approaching traffic has a 70-mph speed limit, a safe crossing sight distance of 760 feet is warranted. This assumes an 85th percentile speed of 74 mph. For freeway on-ramps with prevailing approach speeds of 45 mph, a sight distance of 460 feet would be needed.

The volumes of ramps to be crossed by a bicycle must provide adequate gaps to make a safe crossing. Bicyclists should not be given access to cross ramps with repeated peak hour volumes at or above 500 vehicles per hour.

High-volume ramps and locations without safe crossing sight distances need to be signed to require that bicyclists leave the freeway. Multilane ramp crossings, weave areas, and areas where a bicycle may be forced to approach an on-ramp that does not meet the ramp crossing criteria cited above need to be closed to bicycle travel. Alternate routes should be provided.

INTRODUCTION

Purpose

Currently, 948 of the total 4,224 miles of freeway in California are open to bicycles. Often, bicyclists need access to freeways to reach their destinations. Current California Department of Transportation (Caltrans) policy states, "When a suitable alternate route does not exist, a freeway shoulder may be considered for bicycle travel." Bridges and tunnels, as well as many rural freeway sections, often do not have suitable alternative routes.

The lack of an alternative route should not be the only variable considered when determining whether a freeway is fit for bicycle travel. Unfortunately, no common methods or criteria currently are being employed to measure how well a given section of freeway is suited for bicycles. Caltrans policy leaves the final determination with the local district, offering several roadway factors to consider.

Initially, many people think the idea of allowing bicycles on freeways is ludicrous, and the majority of motorists are completely unaware that bicycles ever are allowed on freeways. Further analysis of the subject, however, reveals that not only do bicycles have access to some freeways, but they are actually encouraged to ride in some areas, such as the Pacific Coast Bike Route. Despite the history of bicycles on freeways, it is difficult to assess the success of allowing bicycle access.

The purpose of this study is to attempt to clarify some of the issues pertaining to bicycles on freeways. Specifically, the goal of this project is to "develop recommendations, guidelines, and policies for bicycle and pedestrian use of freeways, expressways, tunnels, and toll bridges in California." Although pedestrians and bicycles are hardly similar, the nature of the study allowed pedestrians to be analyzed without excessive extra effort.

Background

During the Richmond-San Rafael Bridge Public Access Feasibility Study, Caltrans agreed to sponsor a statewide study defining use and collision data for pedestrians and bicycles on freeway shoulders, including toll bridges and tunnels. On March 30, 1999, representatives of the California Highway Patrol (CHP), bicycle advocacy groups, and Caltrans met to identify a format for the study. From this meeting, the following issues were identified for study:

How safe is the nonmotorized use of shoulders on freeways, tunnels, bridges, and expressways? How is the degree of safety on these facilities determined, measured, and evaluated? What level of safety is acceptable for nonmotorized usage?

Is safety the same for urban freeways and rural freeways? Should they be evaluated differently?

What special factors for bicyclist/pedestrian safety are there through interchanges and on/off-ramps?

How should usage data be collected and evaluated? Should the collision rate for bicyclists/pedestrians be the same as for vehicles? Is the collision rate for bicycles based on miles traveled or exposure? How are bicycle collision rates compared to vehicle collision rates?

When/where would pedestrians be allowed to use freeway shoulders?

Are there any bridges nationwide that allow bicycle access and are they comparable to those in the San Francisco Bay Area?

How are the characteristics of the expected users factored into access decisions?

How important are recovery areas for bicyclists/pedestrians using freeway shoulders?

What data is to be collected and what will be the eventual usage?

In January of 2000, the Mineta Institute of Surface Transportation Policy Studies at San José State University contracted with The Research Foundation at California State University, Chico, to complete the study. The project began immediately, due to a tight time frame. A draft final report for peer review was delivered in September 2000.

The study budget and time frame did not permit extensive counting of bicycles and pedestrians; however, some counting of bicycles was done. Seasonal variations could not be established with a study period substantially under one year. Any existing pedestrian and bicycle count data were utilized as they were discovered. Very little count data became available.

The study encompassed freeways, expressways, toll bridges, and tunnels. The directive was to use data on expressways to help determine the best manner, if any, to accommodate bicycles and pedestrians on freeways. While freeways were to be the focus of the study, toll bridges and tunnels also were included.

A freeway is a limited-access highway with several significant characteristics:

Vehicles traveling in opposite directions are separated by a continuous unpaved median or fixed barrier

There are at least two lanes in each direction

At-grade crossing conflicts are not allowed

Vehicles enter and exit a freeway with merge, diverge, and weave movements.

After the study began, continual guidance and input was received from a steering committee. Progress of the project was presented in the form of six working papers, which served as the basis of this report. Each working paper was delivered to the steering committee with a request for comments. Replies were taken into consideration when writing the final report. Three steering committee meetings were held over the course of the study.

The first steering committee meeting was held on Thursday, February 10, 2000, in Sacramento. The main focus of this meeting was to formulate a final work plan.

The second steering committee meeting was held in San Diego on Monday, April 24, 2000, during a State Office of Traffic Safety summit. A working paper on the literature search relating to bicycle transportation was distributed and discussed at this meeting. The committee also was asked for, and offered, additional bridge and tunnel sites for study.

The final steering committee meeting was held on Friday, August 25, 2000, in Sacramento, to address project recommendations. A policy recommendations working paper was distributed to the committee; major findings and recommendations were discussed.

The draft final version of this report was submitted to the Mineta Institute for Transportation Policy Studies in September 2000. Peer reviews were conducted at the California Department of Transportation and by an anonymous reviewer. Complete peer reviews were returned to the authors in April 2001. The draft final report was adjusted, edited, and improved based on the reviews. This final report is the result.

Study Contents

Chapters 2 through 6 of this study present independent research efforts.

Chapter 2, the survey and literature search, describes studies pertaining to bicycles and pedestrians on freeways, but there is a lack of general knowledge on the subject. Numerous references are summarized, and the policies relating to bicycles on freeways of other states are reported.

Chapter 3 contains a study of Santa Clara County expressways, using the Statewide Integrated Traffic Records System (SWITRS) collision data. The objective of this study was to attempt to find trends in the collision data.

A summary of bicycle and pedestrian collisions on freeways can be found in Chapter 4. Caltrans Districts 1, 2, and 3 were selected for this study. The purpose of this work was to gain insight into the locations and movements proceeding collision of these specific types of freeway collisions. The Traffic Accident Surveillance Analysis System (TASAS) and actual traffic collision reports were the main source of collision information for this chapter.

A look at bridges and tunnels that allow bicycle access can be found in Chapter 5. Several structures from California, along with two bridges from out of state, were studied. Collision history and bridge geometry were compared and analyzed in the search for trends that might contribute to the collision experience on these structures.

Caltrans Districts 5 and 6 were the subject of a statistical analysis found in Chapter 6. An extensive database of freeway geometry, collision rates, and traffic volumes was created and analyzed. Allowing bicycle access to the freeway was an independent variable. The focus of Chapter 6 is to determine if there was any correlation between bicycle access and collision rates as reported by TASAS. Application of Caltrans' bicycle-on-freeway policy was also reviewed.

Chapter 7, the policy recommendations, is the culmination of the results from each of the aforementioned studies. This chapter presents the major findings of this report and suggests data collection that could be employed in the future to improve studies of bicycle transportation on major roadways.

SURVEY AND LITERATURE REVIEW

Introduction

The goal of the survey questionnaire and literature review was to identify existing information relating to bicycle and pedestrian use of major roadways such as freeways, toll bridges, tunnels, and expressways, and to evaluate their safety history on these roadways.

This research utilized the University library, its intra-library loan program, and the Internet to obtain and/or review information possibly pertinent to this study. A number of sources--including documents from various United States (U.S.) State Departments of Transportation (DOT), U.S. government agencies especially, and any bicycle- or pedestrian-related studies, foreign transportation agencies, and bicycle-related periodicals--were used to gain information applicable to this portion of the study.

An important facet of this review was a survey questionnaire that was forwarded to state DOTs, foreign DOTs, and selected bicycle advocacy groups. The focus was to determine whether bicycles and pedestrians were allowed on freeways in specific locations, and to obtain data and information on collisions. An overview of the survey approach and a summary of the survey results are included in this chapter. Although there was only a limited response to the survey, it aided in providing additional supporting information to the literature review. No responses were received from foreign DOTs.

In order to develop a fundamental understanding of the interaction between bicycles, pedestrians, and motor vehicles on high-speed roadways, the following issues were analyzed: bicycle rider characteristics, geometric and physical concerns, collision typologies, collision statistics, current policy, and suggestions for accommodating bikes on high-speed facilities. All pertinent information gathered as part of the literature review and survey questionnaire is presented in this chapter.

Survey

The survey questionnaire that was conducted as part of this study aided in providing some reference material from state DOTs, other highway agencies, and bicycle advocacy groups. The approach to conducting the survey and the survey questions and results are provided in this section.

Survey Approach

A questionnaire with three parts was developed. The first part contained questions regarding the recipient's contact information. The second and third parts were directed toward obtaining information on freeway use by bicyclists and pedestrians, respectively, and any related collision data. The questions posed to state DOTs are shown in Figures 2-1 and 2-2. Questions to bicycle advocacy groups were slightly different in form. The focus of the questionnaire was on obtaining any available information on standards and collision statistics.

An attempt was made to contact the appropriate person to complete the survey at all U.S. state DOTs, 12 bicycle advocacy groups, and four toll road authorities, as well as DOTs and advocacy groups in six English-speaking foreign countries. The contact names were obtained from different sites on the Internet. In the case of the state DOTs, the target contacts were bicycle and pedestrian program coordinators, design standards coordinators, or research directors.

If the contact at a state DOT was a bicycle or pedestrian program coordinator, a survey was sent to that person, and a request was made to pass the survey on to the appropriate person if the contact person could not complete the questionnaire. In other cases, a letter was sent to the contact requesting contact information for the appropriate person. If there was a response, a survey was sent out. In the case of the remainder of the state contacts, a letter and a survey were sent out and a request made to either complete the survey or pass it on to the appropriate person. Bicycle advocates and representatives of foreign countries were asked to pass the survey on to an appropriate person. Most of the communication was handled via e-mail. The State of Oregon, for which relevant information was obtained in another part of the study, was not included.

Survey Questions

Survey Results

Fourteen state DOTs and three toll road authorities responded:

Literature Review

The literature review includes background information on bicycle rider characteristics, geometric and physical concerns, collision typologies, and collision statistics. Information concerning pedestrians is incorporated, where appropriate. Current policy for bicycle and pedestrian use of multilane high-speed facilities is also included.

Bicycle Rider Characteristics

The following are some characteristics of those riders who frequently ride on and will benefit from access to high-speed facilities such as toll bridges and tunnels.

Geometric and Physical Concerns

Special physical concerns that should be considered when designing for bicycle use of high-speed facilities are aerodynamic forces and pavement surface conditions.

Collision Typologies

Due to the tremendous difference in speed and mass of individual bicycles and motor vehicles, collisions between the two tend to be severe. This section attempts to define and identify the different crash types that can occur between the two vehicles.14

John Forester identifies five different maneuvers that lead to collisions between bicycles and motor vehicles on straight sections:

Hitting bicyclist from behind.

Partially overtaking and sideswiping bicyclist.

Motorist overtaking and stopping or slowing in front of bicyclist.

Hitting bicyclist from the front--the motorist from the opposite direction in the cyclist's lane to overtake.

An increased hazard caused by motorists who overtake a bicyclist safely but allow too little clearance to compensate for mistakes by either party or unexpected wind gusts or road surface conditions.15

Collision Statistics

A respectable amount of statistical information on bicycle collisions is available in past publications. Unfortunately, due to the nature of bicycle collisions, the statistics are often varied and hard to compare. This treatment of collision statistics will start with the classification of bicycle collisions, then will look at the proportion of severe collisions, and finally complete an analysis of factors influencing bicycle collisions.