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Case Study

Evaluation of Shared Lane Pavement Markings, San Francisco, CA

City: San Francisco
State: CA
Associated Publication: Urban Bikeway Design Guide

In 2004, the San Francisco Department of Parking and Traffic conducted a study on the effects of different types of shared lane markings on cyclist and motorist behavior. Using before and after videotape data, the city investigated the impact of three different markings- bike-in-house, bike & chevron, and bike & separate arrow- to evaluate how each effected a cyclist’s lateral position in the roadway and motorist behaviors. The six sites included in the study were Polk St., 17th St., 2nd St., Market St., JFK Drive, and Stanyan St. Each of these roadways had a moderate-to-high Average Daily Traffic (ADT) level and was heavily used by recreational and utilitarian cyclists. The centerline of each marking was placed 11’ from the curb and 4’ from parked cars.

The study made several conclusions regarding the positive impacts of shared lane markings. On average, cyclists increased their riding distance to parked cars by 8’’, thus reducing the risks of dooring.  In the presence of passing cars, this margin increased by 3 to 4”. The bike and chevron symbol proved most successful in the study, though all of the markings increased motorists’ awareness of cyclists.

San Francisco Shared Lane Pavement Markings: Improving Bicycle Safety