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Do bicycle lanes improve safety for bicyclists?

The overall safety of on-street bicycle lanes is a highly debated topic. Those in favor of bike lanes argue that they improve safety because they encourage cyclists to ride in the correct direction, signal to motorists that cyclists have a right to the road, and remind motorists to look for cyclists when turning. However, others argue that bike lanes create a false sense of security for cyclists and that drivers easily overlook bike lanes.

Image: Carl Sundstrom

While there are data for perceived safety, and surrogate (behavioral) measures — such as bicyclist direction of riding, sidewalk riding, and distance between passing motorists and bicyclists — that suggest improved safety, we don't have actual measures of safety effects via crash outcomes, and even the surrogate measures are not conclusive. Measuring impacts on bicyclist safety is a difficult undertaking as bicycle crashes with motor vehicles are relatively infrequent occurrences. In addition, exposure data, or data about the amount of bicycling and under what conditions, is sparse. Even less is known about many bicyclists crashing due to bicycle-only falls, crashes with fixed objects, pedestrians, or other bicyclists — data that, as far as we are aware, are not presently being captured in most localities. Certainly, providing space for bicyclists to ride on the roadway would seem to lessen the chances of conflicts and crashes with pedestrians and objects, and possibly the types of collisions involving motor vehicles overtaking bicyclists, especially compared with insufficient shared roadway space or no bicycle facility.

Image: Laura Sandt

There is also no study that shows any evidence that striping bike lanes on busy roads encourages children to ride and get hit on roads that are too dangerous for them. Parents still have to teach their kids where and when they should ride; safe routes to school should still be provided. The AASHTO Guide for the Development of Bicycle Facilities clearly says that one type of facility is not going to suit all riders all of the time.

Most critics note that bike lane safety depends heavily on drivers being attentive to the cyclists. Drivers parking in spaces adjacent to bike lanes need to check for cyclists when pulling into the space, opening their doors, or pulling out into traffic. A common and often severe car-bike collision is the "right hook," in which a driver turns right across a bike lane, without first looking to see if that lane is occupied. In these crashes, cyclists have very little time to react and may end up underneath the vehicle. Hazards such as these require that cyclists riding in bike lanes be attentive and anticipate drivers' actions as much as possible.

Image: Dan Burden

The safety of bike lanes also depends on their design. Transportation engineers are vigilant to ensure that bicycle lanes conform to ITE and AASHTO standards. Some cities are applying a new design concept, the sharrow, where inadequate space exists for bike lanes. Other agencies have used more innovative techniques to enhance bike lane markings, such as using blue or green paint to continue a bike lane through an intersection. One study in St. Petersburg, Florida, found that a combination of green paint and signing resulted in increased motorist yielding to bicyclists.

Providing space through bike lanes, wide outside lanes, or paved shoulders allows room for bicyclists to be overtaken safely by faster-moving motor vehicles. Obtaining sufficient before and after data, as well as data from comparison sites, to measure the safety impacts of bicycle lanes will require a huge effort and resources that, thus far, have not been available.

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