Determinants of Bicycle Crashes at Urban Signalised Intersections: Preprint

Problem Bicycle volumes are increasing in many regions worldwide leading to higher relevance of an in-depth understanding of bicyclist safety mechanisms. Detailed studies on bicyclist safety that consider exposure and distinguish by intersection category and crash types are missing for urban signalised intersections which are of particular relevance for bicyclist safety. Method Based on a comprehensive dataset of motorist and bicyclist volumes and infrastructure characteristics for a sample of 269 signalised intersections in two German cities, we analyse in a top-down approach first bicycle crashes of all types and second bicycle crashes by type including turning, right-of-way and loss-of-control. A combination of descriptive statistics and Accident Prediction Models (APM) are applied in terms of analysis methods. Results Bicycle volumes are relevant for all types of intersections and crashes whereas the effect of motor vehicle volumes differ between these different applications. The separation of bicyclists from motor vehicles in time and space increases their safety but also leads to behavioural adaption and risk compensation. The likelihood of right-ofway crashes even increases with more separation in the signalling scheme. The main predictor for loss-of-control crashes in terms of infrastructure are tram tracks. Summary This study provides insights on relevant determinants of bicycle crashes at urban signalised intersections at several levels of detail. Exposure variables as well as the physical separation of bicyclists from motor vehicles show consistent effects on bicycle crash numbers whereas the effects of signalling differ between crash types. Practical Applications The different types of intersections and crashes follow each specific mechanisms of bicyclist safety. The separation of bicyclists and motorists in time and space are paramount at intersections with high bicycle volumes. Risk compensation such as red light running becomes more important as intersections get smaller and motor vehicle volumes decrease