Corridor-Level Signalized Intersection Safety Analysis in Shanghai, China using Bayesian Hierarchical Models

摘要

Most traffic crashes in urban areas of Chinese cities occur at signalized intersections.Research on the intersection safety problem in China is still in its early stage. Therecent development of an advanced transportation information system in Shanghai nowenables in-depth intersection safety analyses using road design, traffic operation andhistorical crash databases. In the urban areas of Shanghai, the road network density isrelatively high and the distance between signalized intersections is small, averaging199 meters. Adjacent signalized intersections located along the same corridor sharesimilar traffic flows, and signals are usually coordinated with each other. Therefore,when considering intersection safety in Shanghai, it is essential to account for thecorrelation among intersections within the same corridor. In this study, data for 195signalized intersections along 22 corridors in urban areas of Shanghai were collected.Operating speeds along these corridors were anticipated to be an important predictor ofcrashes. Average speeds and speed variances of corridors were acquired from taxisequipped with Global Positioning Systems (GPS). Bayesian hierarchical models wereapplied to identify crash risk factors at both the intersection and the corridor levels.Results showed that average speed was a significant factor affecting safety and thatintersections along corridors with lower average speeds were associated with fewercrashes than those with higher speeds. It was found that intersections along two-wayroads, under elevated roads, and in close proximity to each other, tend to have highercrash frequencies.