Environmental Practice


RESEARCH ARTICLE: Evidence on Why Bike-Friendly Cities Are Safer for All Road Users

Wesley E. Marshalla1 c1 and Norman W. Garricka2

a1 University of Colorado Denver, Department of Civil Engineering, Denver, Colorado

a2 University of Connecticut, Civil & Environmental Engineering, Storrs, Connecticut


Biking is increasingly being recognized as a highly sustainable form of transportation. Consequently, a growing number of American cities have seen tremendous growth in bicycle travel, in part because many cities are also investing resources into improving bicycling infrastructure. Aside from the environmental advantages, there is now growing evidence to suggest that cities with higher bicycling rates also have better road safety records. This study attempts to better understand this phenomenon of lower fatality rates in bike-oriented cities by examining 11 years of road safety data (1997–2007) from 24 California cities. The analysis included accounting for crashes across all severity levels, as well as for three classes of road users: vehicle occupants, pedestrians, and bicyclists. Additionally, we looked at issues of street and street network design to help determine the role that these features might play in affecting both bicycling rates and road safety outcomes. Overall, cities with a high bicycling rate among the population generally show a much lower risk of fatal crashes for all road users when compared to the other cities in our database. The fact that this pattern of low fatality risk is consistent for all classes of road users strongly suggests that the crashes in cities with a high bicycling rate are occurring at lower speeds. This agrees with the finding that street network density was one of the most notable differences found between the safer and less safe cities. Our data suggest that improving the streets and street networks to better accommodate bicycles may lead to a self-reinforcing cycle that can help enhance overall safety for all road users.

Environmental Practice 13:16–27 (2011)

(Online publication April 06 2011)


c1 Wesley E. Marshall, PhD, PE, Department of Civil Engineering, University of Colorado Denver, 1200 Larimer Street, Campus Box 113, Denver, CO 80217-3364; (phone) 303-352-3741; (fax) 303-556-2368; (e-mail) wesley.marshall@ucdenver.edu

Wesley Marshall is an assistant professor of civil engineering at the University of Colorado, Denver (UCD), and codirector of the Active Communities Transportation (ACT) Research Group. He is also an affiliated faculty member of the UCD Center for Sustainable Infrastructure Systems (CSIS). He specializes in transportation research dedicated to building a more sustainable infrastructure, particularly in terms of road safety, active transportation, transit-oriented communities, congestion pricing, and parking. His recent research involves defining and measuring the street network and an empirical study considering the role of street patterns, connectivity, and network density in road safety and sustainability. Having spent time with the University of Connecticut Center for Transportation and Urban Planning, Sasaki Associates, and Clough, Harbour and Associates, Wesley is a native of Watertown, Massachusetts, a graduate of the University of Virginia, and he received his PhD in transportation and urban engineering from the University of Connecticut. He is also a recipient of the Dwight D. Eisenhower Transportation Fellowship and the Charley Wootan Award for best Transportation Research Board (TRB) paper.

Norman Garrick is Associate Professor of Civil Engineering at the University of Connecticut and a member of the national board of the Congress for the New Urbanism (CNU) and the Tri-State Transportation Campaign. He specializes in the planning and design of urban transportation as they relate to sustainability and urban revitalization. In addition to his academic and research career, Norman has worked as transportation consultant on a number of design charrettes, nationally and internationally, including urban revitalization projects with the Prince of Wales Foundation in Kingston, Jamaica, and Freetown, Sierra Leone. He is a 2008 recipient of the Transportation Research Board's Award for Best Paper and a 2004 Fulbright Fellowship to Jamaica.