Exploring Spatial Non-Stationarity and Varying Relationships between Crash Data and Related Factors Using Geographically Weighted Poisson Regression

The spatial nature of crash data highlights the importance of employing Geographical Information Systems (GIS) in different fields of safety research. Recently, numerous studies have been carried out in safety analysis to investigate the relationships between crashes and related factors. Trip generation as a function of land use, socio-economic, and demographic characteristics might be appropriate variables along with network characteristics and traffic volume to develop safety models. Generalized Linear Models (GLMs) describe the relationships between crashes and the explanatory variables by estimating the global and fixed coefficients. Since crash occurrences are almost certainly influenced by many spatial factors; the main objective of this study is to employ Geographically Weighted Poisson Regression (GWPR) on 253 traffic analysis zones (TAZs) in Mashhad, Iran, using traffic volume, network characteristics and trip generation variables to investigate the aspects of relationships which do not emerge when using conventional global specifications. GWPR showed an improvement in model performance as indicated by goodness-of-fit criteria. The results also indicated the non-stationary state in the relationships between the number of crashes and all independent variables.