Mapping bicycling exposure and safety risk using Strava Metro

Colin Ferster,Trisalyn Nelson,Karen Laberee,Meghan Winters

doi:10.1016/j.apgeog.2021.102388

Colin Ferster, Trisalyn Nelson + Show 2 more

Open Access

https://doi.org/10.1016/j.apgeog.2021.102388

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Abstract

Overcoming concerns about bicycling safety is critical to increasing the health benefits of bicycling for transportation. While exposure measures are critical for monitoring and understanding bike safety, lack of spatially and temporally detailed bike counts makes it challenging to conduct robust bicycling safety studies. Crowdsourced data from smartphone apps like Strava provide counts for nearly all individual road and trail sections with 1-min temporal resolution. Researchers have found that patterns of Strava bicyclists are similar to all bicyclists in our study area. In this paper, we develop and test a method to normalize bike safety incident hotspots using exposure estimated from Strava data for Ottawa, Canada. We mapped incident hotspots normalized by exposure at increasingly detailed temporal scales. In a dataset with more than more than 8 million Strava activities and 395 incidents (approximately 20,000 Strava activities per incident), adjusting for exposure moved incident hotspots away from protected bike lanes and multi-use paths and onto commercial streets with no bike infrastructure. Strava data are available to correct for exposure where other measures are not available. We encourage researchers, planners, and public health practitioners to consider crowdsourced data to fill exposure data gaps and provide context for interpreting incident data.

Highlights

To increase access to the health benefits of bicycling it is important to overcome safety concerns of bicyclists and potential bicyclists
Our goal is to develop and test a method of identifying and normalizing bike safety incident hotspots using exposure estimated from Strava data
The largest raw incident hotspots were located in the downtown core along Laurier Avenue, where there is a protected bike lane (Fig. 1a)

Summary

Introduction

To increase access to the health benefits of bicycling it is important to overcome safety concerns of bicyclists and potential bicyclists. Robust bicycling safety research is needed but is often limited by lack of exposure data. Without exposure data safety studies cannot determine the cause of high numbers of crashes or near misses, which could relate, for example, to an infrastructure issue or be attributable to a large number of bicyclists. As with motor vehicle safety, exposure data allow for the calculation of risk to determine the incident rates per trip or per kilometer traveled, enhancing the contextual interpretation (Kweon & Kockelman, 2003; Vanparijs, Int Panis, Meeusen, & De Geus, 2015). Lack of consideration of exposure can result in misleading con clusions when comparing locations across a city and is problematic for safety monitoring. If new bicycle infrastructure results in an increase in the number of bicyclists, the total number of bicycling incidents could increase even while the actual rate of bicycling incidents declines

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