Factors Affecting Classification of Road Segments into High- and Low-Speed Collision Regimes

The safety of locations operating under high-speed conditions could significantly differ from that of locations operating under low-speed conditions. Therefore, different approaches must be adopted when speed and safety are analyzed and managed at locations operating under different regimes. However, it is necessary first to understand the factors affecting the speed–collision classification of a site. Locations operating under high speeds are typically expected to have more collisions compared with locations in which speeds are low. Some locations, however, might experience a high collision rate even when speeds are low, or vice versa. This study aimed to identify the factors that affected the site classification into any of those categories by using data collected on roads in Edmonton, Alberta, Canada. Locations were divided into four speed–collision bins (high collision, high speed; high collision, low speed; low collision, high speed; low collision, low speed), and geographic information system maps of locations were produced to explore the spatial distribution of those locations. Moreover, logistic regression was used to understand the role of different factors in identifying the speed–collision bin to which a certain location belonged. The results reveal that locations with high collision rates but low speeds have a relatively high population of heavy vehicles and trucks as well as high speed variability. As for locations with low collision rates and high speeds, these sites were found to have a high level of protection through the presence of medians and shoulders with relatively low access density.