How are "Sharrows" or shared-lane markings used to improve bicyclist safety?

At present, shared-lane markings are not in the Manual of Uniform Traffic Control Devices (MUTCD) and thus are considered by the Federal Highway Administration (FHWA) to be an experimental treatment (there is a bicycle technical committee of the National Committee for Uniform Traffic Control Devices [NCUTCD] recommendation to incorporate guidelines for a particular shared-lane marking in the next edition of the MUTCD). Shared-lane markings may be used to indicate a bicyclist's preferred path of through travel when bicyclists and motorists must share a lane. Prior experimentation from San Francisco and guidelines for language to be incorporated in the next MUTCD suggest that shared-lane markings may help to improve bicyclist and bicyclist-motorist positioning in shared-lane situations. The markings should be used only when roadway alignment, operational, or other conditions do not allow striping a bike lane. Of the designs that have been used in various communities, the recommended marking at present is known as the bike and chevron design and is as shown.

A bicyclist rides on a roadway marked with a sharrow in San Francisco, California.

Shared-lane stencils may help keep bicyclists from riding too close to parked cars (to help prevent dooring crashes) or too close to the curb or roadway edge where broken pavement, drainage grates or other hazards may contribute to crashes. They may also promote safer passing by motorists. Good uses of shared-lane markings may be to bridge gaps between disconnected bike lanes in locations where bike lanes cannot be striped, to indicate an intermittent shared lane situation where there is insufficient room to overtake within the same lane, or to indicate the proper bicyclist travel path in a wide outside lane situation. The presence of sharrows may also be an indicator to motorists to be more aware of bicyclists on the roadway. Additional planned and ongoing research should help to provide more guidance on where and how shared lane markings may be used to improve bicyclist safety.

Learn more about on-street biking facilities in our engineering section.