JOHN S. ALLEN'S BICYCLE FACILITIES, LAWS AND PROGRAMS PAGES

Bicycle sidepaths: crash risks and liability exposure

Evidence from the research literature

The evidence that bicycling on sidewalks and similar facilities is more hazardous than bicycling on streets is overwhelming. Need to see that evidence? Here are some graphs, and links to studies posted on the Internet on this site and others:

Adult Bicyclists in the U.S. by Dr. William Moritz. Relative danger index 24.8 times as high for sidewalk riding as for major street without bicycle facilities. (Data include all crashes, not just car-bike collisions). The population was avid adult recreational and utility cyclists. The following graph by Martin Pion summarizes the results for different facility types.

A Survey of North American Bicycle  Commuters by Dr. William Moritz   Relative danger index 5.32 times as high on "other" facilities (mostly sidewalks) as on average of all facilities (mostly streets). Data include all crashes, not just car-bike collisions. Lower ratio than in previous study probably related to typically lower speed and overall higher crash rate of average commuters compared with avid cyclists.

The Risks of Cycling by Dr. Eero Pasanen, Helsinki, Finland. Small samples, but results consistent with other studies:

Higher car-bike collision rate for one-way sidepaths compared with streets, even though pedestrians are prohibited from the sidepaths. Higher rate yet on sidewalks. Rate on sidepaths 4 times as high as on paths away from streets.

2.5 times as high rate when crossing intersection from sidewalk compared with street, 2.9 times as high when crossing from path.

Extremely high rate of car-bike collisions with bicyclists crossing intersection on the left sidepath.

1987 study by the University of Lund, Sweden. (summarized in a conference report, with an explanation of the diagram below). 11.9 times the risk of car-bike crashes for bicyclists riding on a left sidepath, and 3.4 times for bicyclists on the right sidepath, compared with bicyclists riding in the normal position on the road.

Alan Wachtel and Diana Lewiston, Risk Factors for Bicycle-Motor Vehicle Collisions at Intersections (ITE Journal, September 1994). Car-bike collision rate 1.8 times as high for sidewalk riding as for streets on average, and higher for all categories of cyclists.

Sidewalk Bicycle Safety Issues, by Lisa Aultman-Hall and Michael F. Adams Jr. Bicycle crash rate 6 to 10 times as high on sidewalks as on streets in Toronto. (PDF document. See page 4.)

Toronto Bicycle Commuter Safety Rates, by Lisa Aultman-Hall and M. Georgina Kaltenecker. 4 times as high injury accident rate on sidewalks as on streets (PDF document. See table 5, page 19).

A survey of research on the crash rates of streets, bicycle paths and sidewalks is available on the Internet on John Franklin's site.

A summary of the topic of bicycle accident types and prevention is to be found in the books Effective Cycling and Bicycle Transportation, by John Forester, published by MIT Press.

Liability Aspects

The paper Liability Aspects of Bicycle Environments: Bicycle Facilities and Roads, by three notable experts on bicycle transportation, Alex Sorton, P.E., Tom Walsh, P.E. and John Williams was presented at the Institute of Traffic Engineers 1990 Annual Meeting and specifically recommends against sidewalks and sidepaths as bicycle facilities. Here are extracts from that paper:

A commuter bicyclist was riding on a designated bikeway. This bikeway had been created on the curbside half of an existing 10-foot sidewalk. Signs and markings were used to designate the facility and parking was allowed adjacent to the curb. A driver, while making a right turn into an alley, failed to see a bicyclist on the bikeway, primarily because a parked vehicle blocked the view, and ran over him. The bicyclist was severely injured.

The bicyclist sued the operating agency claiming negligent design. He pointed out that the AASHTO Guide strongly suggests not placing bikeways on a sidewalk adjacent to a street because of the sight obstruction created by parked cars.

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It is all too common to find bicycle accommodations, especially bike paths, whose principal designers have been landscape architects and environmental planners. The only criticism of this design team is the absence of input from the highway and traffic engineering professions. The adequacy of critical design considerations such as surface, grades, curvature, sight distance, and traffic control devices is best determined by a knowledgeable transportation professional.

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Regardless of the designer's expertise, special bicycle accommodations must always reflect current guidelines and sound judgment. Some states have promulgated their own design guidelines, which should be used where applicable. The courts and practitioners have also recognized the 1981 AASHTO Guide [current version is the 1999 AASHTO Guide] and the MUTCD [part 9, which applies to bicycles]. Although there are other available references pertaining to the design, maintenance, and control of bicycle accommodations, these two should be considered "required reading" for transportation professionals responsible for bicyclists' safety and mobility.

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The extent to which bicycles can be integrated with traffic and uncommon features minimized or mitigated without compromising bicycle mobility will determine the success of bicycle accommodation projects.

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Make sure bicycle facilities conform to the 1981 AASHTO Guide [updated version published in 1999; see comments on another page of this site] or other current guidelines.

Failure to meet the guidelines has led to multi- million dollar judgments against agencies. Here are a few important tips from the current AASHTO Guide:

1. Don't put two-way bikeways on one side of a street. Such facilities cause serious conflicts at intersections and driveways. Two-way bike lane use has led to a number of fatal head-on collisions . And such facilities encourage wrong-way riding.

2. Don't designate sidewalk bikeways. These also cause serious car-bike conflicts at intersections and driveways, as well as conflicts between bicyclists and pedestrians. Eugene, Oregon, and other cities have found that sidewalk bikeways have extremely high accident rates.

Copyright 2002, John S. Allen
except quotations, fair use.
Last revised 8 December 2010