Studying the Associations between Street Design Variables and Severity of Injury from Bicycle-Motor Vehicle Crashes

Background: Safety concerns are major barriers to cycling, preventing Americans from gaining the associated significant health benefits. Intersection design variables might contribute to the severity of crashes.  In this study, we examined the associations between environment design variables (i.e. intersection angle, street width) with bicycle-motor vehicle crash severity.

Methods: A total of 3350 crash cases were obtained from New York City (NYC).  The data included geospatial information about each crash location (i.e. latitude and longitude collected with a GPS device by the Police at crash site).  We used the Single Line Street Base Map, the geographic data from the NYC Department of Planning, and GIS techniques to extract information on street factors. Injury severity was classified as severe (incapacitating or killed) or moderate (non-incapacitating). The association between injury severity and environment design variables was examined using multivariate logistic regression analysis.

Results: As compared to orthogonal intersections, the odds of severe injuries were higher for crashes at non-orthogonal intersections (OR 1.40 95% CI 1.01, 1.96), and at non-intersection street segments (i.e. crashes that happened on streets outside intersection proximity) (OR 1.53 95% CI 1.12, 2.08). Road system and street width were not significantly associated with injury severity.

Conclusion: Bicycle-vehicle crashes at non-orthogonal intersections are more likely to result in higher injury severity.  These findings suggest that non-orthogonal intersections and non-intersection street segments may warrant priority for protective interventions such as bicycle signals at intersections or protected bike lanes (i.e. cycle tracks) in non-intersection segments.