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Why are Bike-Friendly Cities Safer for All Road Users?

Despite bicycling being considered on the order of ten times more dangerous than driving, the evidence continues to build that high-bicycling-mode-share cities are not only safer for bicyclists but for all road users. This paper looks to understand what makes these cities safer. Are the safety differences related to 'safety in numbers' of bicyclists, or can they be better explained by differences in the physical places or the people that inhabit them? Based on thirteen years of data from twelve large U.S. cities, the authors investigated over 17,000 fatalities and more than 77,000 severe injuries across nearly 8,700 block groups via multilevel, longitudinal, negative binomial regression models. The authors hypothesize three potential pathways towards better road safety outcomes: i) travel behavior differences (e.g. 'safety in numbers' or shifts to 'safer' modes); ii) built environment differences (e.g. infrastructure that helps promote safer environments); and iii) socio-demographic and socio-economic differences (e.g. as some cities may be more populated by those with lower transportation injury risks). The results suggest that more bicyclists on the road is not the underlying reason these cities are safer for all road users. Better safety outcomes are instead associated with a greater prevalence of bike facilities – particularly protected and separated bike facilities – at the block group level, and even more strongly so, across the city as a whole. Higher intersection density, which typically corresponds to a more compact and lower-speed built environment, was strongly associated with better road safety outcomes for all road users. The variables representing gentrification also accounted for much of the explainable variation in safety outcomes. This first chapter helps support an evidence-based approach to building safer cities for all road users. While the policy implications of this work point to protected and separated bike infrastructure as part of the solution, we need to keep in mind that the potential pathways toward safer cites are complementary and should not be considered in isolation. Moreover, the results – particularly the safety disparities associated with gentrification – suggest equity issues and the need for future research. This report includes four parts: (1) Why Are Bike-Friendly Cities Safer for All Road Users? (2) Assessing Equity and Urban/Rural Road Safety Disparities; (3) Age-Specific Bicycling Safety Trends, 1985-2015; and (4) Advancing Healthy Cities Through Safer Cycling: An Examination of Shared Lane Markings.

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  • Supplemental Notes:
    • This document was sponsored by the U.S. Department of Transportation, University Transportation Centers Program.
  • Corporate Authors:

    University of Colorado, Denver

    Department of Civil Engineering
    1200 Larimer Street, P.O. Box 173364
    Denver, CO  United States  80217-3364

    Mountain Plains Consortium

    Civil & Environmental Engineering
    122 S. Central Campus Drive
    Salt Lake City, UT  United States  84112-0561

    Upper Great Plains Transportation Institute

    North Dakota State University
    1320 Albrecht Boulevard
    Fargo, ND  United States  581052

    Office of the Assistant Secretary for Research and Technology

    University Transportation Centers Program
    Department of Transportation
    Washington, DC  United States  20590
  • Authors:
    • Marshall, Wesley E
    • Ferenchak, Nick
    • Janson, Bruce
  • Publication Date: 2018-12

Language

  • English

Media Info

  • Media Type: Digital/other
  • Features: Appendices; Figures; Maps; Photos; References; Tables;
  • Pagination: 162p

Subject/Index Terms

Filing Info

  • Accession Number: 01692012
  • Record Type: Publication
  • Report/Paper Numbers: MPC 18-351
  • Contract Numbers: MPC-455
  • Files: UTC, NTL, TRIS, ATRI, USDOT
  • Created Date: Jan 31 2019 5:17PM