Assessing the Impact of Sharrows on Bicyclist Behavior: A three-year natural experiment in Santa Ana, California

Bicycle infrastructure preferences vary by rider experience and comfort, yet both bicyclists and motorists perceive separated bicycle lanes as safer than shared lane markings (sharrows). Despite widespread adoption, evidence on the real-world behavioral impacts of sharrows remains limited. This study evaluates a natural experiment in Santa Ana, California, where sharrows were installed in a downtown commercial corridor when separated bicycle lanes were not feasible. Researchers collected baseline data in September 2015 and follow-up data in February 2016 and early 2017, totaling 54 hours of direct bicycle observation across two target areas. Results revealed a mixed and cautionary pattern of change. West-to-East mean bicycle counts increased significantly from 0.986 (2015) to 1.734 (2016; p = 0.045) but declined to 1.500 by 2017. East-to-West counts showed modest, non-significant year-over-year growth. Critically, sidewalk riding increased significantly from 2015 to 2016 (p = 0.002) and remained elevated through 2017 (p = 0.009), and wrong-way riding increased significantly from 2015 to 2016 (p = 0.003). Female ridership declined from 2015 to 2016 (p = 0.036) but recovered by 2017. Ridership among adults over 65 declined post-installation without meaningful recovery. Overall, sharrow installation was not associated with lasting ridership gains or improved safe bicycling behavior. Declines among women and older adults suggest sharrows may not adequately meet the needs of all roadway users. Drawing on the present data and prior literature, policymakers should consider pairing sharrows with education programs, driver awareness campaigns, and enhanced infrastructure to support safety, equity, and sustained bicycling engagement.