Crash Rate Analysis

A crash rate is a measure that can be used to quantify the safety risk experienced by an individual pedestrian or bicyclist at a specific location, in a roadway corridor, or throughout a campus community. Example crash rates include pedestrian crashes per million pedestrian roadway crossings at an intersection, bicycle crashes per million bicyclists using a roadway corridor, pedestrian crashes per hundred hours of walking in the campus area, or bicycle crashes per thousand miles bicycled throughout a campus community. Note that crash rates can also be calculated for specific times of day, days of the week, and times of year. Crash rates help overcome the limitation that crashes tend to be concentrated in locations and at times with high levels of pedestrian or bicyclist activity. In fact, most studies that use crash rates show that there is actually less risk to each individual pedestrian or bicyclist in locations and at times that have higher levels of walking and bicycling activity.

UC Berkeley Campus Periphery Reported Pedestrian Crash Rates by Time of Day from 2000-2009

UC Berkeley campus periphery reported crash rates by time of day from 2000-2009.
Source: Schneider, Grembek, and Braughton (2013). Pedestrian Crash Risk on Boundary Roadways: A university Campus Case

Considerations: Pedestrian and bicycle crash rates can be challenging to calculate because they require exposure data (e.g., intersection or screenline counts, time or distance traveled, model-estimated volumes). In addition, if crash rates are the only criterion used to select locations for pedestrian or bicycle safety treatments, some of the improvements may be made in high-risk locations that have very few pedestrians or bicyclists.

Application: Schneider, Grembek, and Braughton (2013) analyzed pedestrian crash risk at roadway intersections bounding the University of California, Berkeley campus. While the highest number of pedestrian crossings was in the daytime, they found that pedestrian crash risk near campus was highest in the evening and at night (see below).

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