Exploring factors influencing crash injury severity on freeways using ordered probit model

The crash injury severity has long been researched and discussed as a significant part of traffic safety. Various factors, in the areas of geometrical design, traffic flow and environment, have been taken into consideration using diverse models. Purpose of the paper is to explore and analyze factors that greatly influence probability of severe accident´s occurrence. The fully developed ordered probit model was adopted in this paper. Explained by 9539 accident data on a freeway in Guangzhou, China, result of the model shows that six variables are significant. Among them, increase of length, horizontal curve existence and number of lanes have positive effects to a severer crash, while road width in one direction, average flow rate per year and speed limit have negative influence. The finding of the research can be applied to improvement of traffic safety, especially on freeways.