Epidemiology and spatial examination of bicycle-motor vehicle crashes in Iowa, 2001-2011

Purpose: To identify how person, crash, environment, and population characteristics differ between bicycle-motor vehicle crashes that occur at intersections and non-intersections. Methods: The Iowa Department of Transportation crash database for the years 2001 through 2011 was used to identify bicycle-motor vehicle (BMV) crashes and associated person, crash, and environment characteristics. Population-level data were drawn from the 2010 U.S. Census and the 2010 American Community Survey. Descriptive statistics, GIS mapping, and multivariable logistic regression were used to examine factors associated with crash risk and crash location. Results: Compared to intersections, non-intersection BMV crashes had higher odds of involving young bicyclists (<10 years old; OR: 1.8, 95%CI: 1.2-2.6), location outside city limits (OR: 5.7, 95%CI: 3.9-8.3), with driver vision obscured (OR: 1.5, 95% CI: 1.2-1.8), reduced lighting on roadway (OR: 1.9, 95% CI: 1.5-2.4), and lower odds when the bicyclist (OR: 0.4, 95% CI: 0.3-0.6) or motorist (OR: 0.6, 95% CI: 0.4-0.8) failed to yield right of way. Conclusions: Environmental factors, as well as developmental (age) and behavioral factors of bicycle-motor vehicle crashes vary by location (intersection/non-intersection). Results from this study can be used to tailor and target multiple intervention approaches, such as making infrastructure changes, increasing safety behavior among both motorists and bicyclists, and identifying which age groups and locations would most benefit from intervention.