Exploring the Roles of Conformity, Hazard, & Convenience in Risk Mitigation Decisions: An Observational Study of Helmet Use Among Bicyclists and E-scooter Riders in Los Angeles During Two Natural Experiments

Sparks, Adam M., Daniel M. Fessler, and Marlee Zinsser. 2019. “Exploring the Roles of Conformity, Hazard, and Convenience in Risk Mitigation Decisions: An Observational Study of Helmet Use Among Bicyclists and E-scooter Riders in Los Angeles During Two Natural Experiments.” PsyArXiv. October 7. doi:10.31234/osf.io/gspbm

Abstract: Despite the protection offered by bicycle helmets, their use varies substantially across populations of riders. Building on previous efforts to understand helmet use as reflecting tradeoffs between convenience and safety, we explore whether helmet use is influenced by conformity, that is, by a preference to make the same helmet use decision as other riders. If so, an experiment introducing more riders with or without helmets in a specific location might shift helmet use patterns among other nearby riders. We conducted an observational study of helmet use over eight months at five locations across two university campuses in Los Angeles, California, U.S.A. During this time, a bikeshare program and electronic scooter rental services were introduced in the local area. The low use of helmets among riders of these vehicles allow us to treat these as natural experiments testing the conformity hypothesis. Corresponding to the sudden appearance of numerous helmetless e-scooter riders, helmet use declined among riders of ordinary bicycles at the more hazardous study locations, a pattern we cautiously interpret as consistent with a conformity preference among ordinary cyclists traveling long distances along city streets among helmetless e-scooter riders. At the safer locations, helmet use rates increased among ordinary cyclists, which we suggest was driven by vehicle selection decisions, with the most convenience-oriented riders preferring to use e-scooters, leaving a more safety-oriented population of ordinary cyclists. The possibility that social conformity may influence risk mitigation decisions has important implications for designing and measuring the impact of public health interventions. Also of note are are empirical demonstrations that helmet use patterns can vary substantially across seemingly similar populations and over short periods of time