Bicycle Injury Interventions

Bicycle Lanes and Paths

Background

Bicycle lanes are defined as portions of the roadway designated for the use of bicycles.36 Where bicycle lane policies exist, shoulder lanes are 1 m wide in each travel direction, separated from the roadway by a minimum buffer distance of at least 0.5 m. This buffer zone is usually increased along sections of road with higher motor vehicle speed. Paved surfaces are required in the few states where bicycle lane policies exist, but most paved shoulders are not intended for bicyclist use. In North America, bicycle traffic is permitted on most highway shoulders in Canada, while bicyclists in the United States are restricted from utilizing interstate highways and limited access highways in most states.37

Bicycle paths are defined as physically separated rights of way for the exclusive use of bicyclists and pedestrians.36Policies regarding bicycle paths could not be found for this review, but are presumed to be similar to bicycle lanes with respect to travel direction width.

Note: no new studies- only Wachtel, 1994 and Lott, 1976 included in previous review.


Review of bicycle lane studies:

Author

Wachtel et al., 1994

Study design and target population

Case control study

Police reports of bicycle accidents in Palo Alto, CA, from July 1985 to June 1989.

Cases: motor vehicle/bicycle collisions at intersections

Controls: observed cyclists during one day in 1987.

Intervention

No real intervention, but did examine risk ratios for MV/bicycle collisions with respect to sidewalk and roadside bicycle use.

Outcomes

Reported MV/bicycle accidents at intersections along three stretches of road in Palo Alto. (Intersections defined as any point where turning or crossing movements are possible for the bicyclist or motorist, including the junctions between driveways and sidewalks, and driveways and roadways.)

Direction of travel among accidents

Results

Older cyclists (>17) have over twice the risk of collisions with motor vehicles compared to younger riders, adjusted for sidewalk/roadway use and wrong-way travel (OR=2.2, 1.6-3.1).

Bicyclists traveling against traffic have a greater risk (OR=3.8, 2.6-5.2) adjusted for age and riding on sidewalk/road.

Study quality and conclusions

Shared use of the roadway in the same direction is associated with a decrease in accident risk between bicycle and motor vehicle.

Sidewalk bicycling adjacent to busy intersections should not be encouraged.

Did not compare accident rates on roads with lanes to roads without lanes.

No controlling for such potential confounders as miles ridden, speed, weather, and road surface.



Author

Lott and Lott, 1976

Study design and target population

Ecological study

Police reports of bicycle-car collisions in Davis, CA, 1970-73 (n=145).

Intervention

Bicycle lane use

Outcomes

Reported bicycle-car collisions stratified into 10 subjective categories (improper left turn by cyclist, motorist failed to yield, etc.).

Frequency of incidents in Davis, CA, (with bike lanes) compared to Santa Barbara, CA (without bike lanes).

Within Davis, CA, frequency of incidents on streets with bike lanes compared to streets without bike lanes.

Results

Bicycle lanes suggest (as a ratio of accident expectation rate with bike lanes to without bike lanes) a protective effect for certain types of bike-car collisions (cyclist exiting driveway, 0.12; motorist exiting driveway, 0.49; improper right turn by motorist, 0.58; cyclist traveling against traffic, 0.26; motorist overtaking cyclist, 0.12) but increase risk of crash when cyclist turns left into traffic (1.8).

Study quality and conclusions

No data on exposure of bicyclists (e.g., miles traveled). Low visibility and nonclassifiable incidents excluded from analysis. Davis, CA, data include non-bike lane incidents. Bike lanes not placed randomly among streets.

Incidents stratified subjectively; no objective basis for determining ‘neutral’ incidents.

Summary of bicycle lane studies

The studies reviewed here present some evidence that bicycle lanes may provide protection against bicycle/motor vehicle collisions. Unfortunately, comparisons between roads with and without bike lanes did not take exposure into account and the conclusions reached are therefore speculative at best. Evidence is also presented that indicates riding with the flow of traffic reduces one’s chance of collision with a motor vehicle. There are some preliminary data indicating that bicycle paths may have an impact on accident rates, but no conclusions can be reached until data collection and analysis are complete.39

Recommendations on effectiveness of bicycle lanes

Where bicycle lanes exist, riding should be restricted to the direction of motor vehicle travel. Paved riding surfaces should be mandatory for bicycle lanes, as well as a wide buffer zone (preferably > 2.0 m) between motor vehicle traffic and bicyclists, increasing in direct proportion to the speed of the motor vehicles. There is some speculatory data that bicycle lane widths should increase if rumble strips are used between motor and bicycle traffic zones40 so that bicyclists do not ride over the strips accidentally.

Recommendations for future research

Randomized controlled trials examining the effectiveness of bicycle paths and/or bicycle lanes are not feasible given the construction cost of such features. To determine whether bike lanes or paths are effective in reducing bicycle accidents not only with other bicyclists and pedestrians but also with motor vehicles, a cohort study design might be implemented comparing two groups of riders–those using a bicycle lane/path (exposed) and those not using the lane/path (unexposed)–and their respective accident incidence rates. This would, however, require large groups of cyclists. The cohort study might also be conducted in which the cohorts are roads versus paths and the rate of crashes calculated for each. This approach would require reliable data on usage of bicycle paths and roads, such as miles traveled.


Harborview Injury Prevention and Research Center 1997 University of Washington Last updated: 09-July-2001