Incorporating Mode Choices into Safety Analysis at the Macroscopic Level

Investigating the contributing factors to aggregated crashes as a function of trip variables combined with details of their purpose and transportation modes is important in the planning stage of a transportation network. The primary purpose of this study is to investigate the association between aggregated crashes, different trip modes, and trip purposes in traffic analysis zones (TAZs). Negative binomial (NB) and a geographically weighted Poisson regression (GWPR) were estimated for total and severe crashes separately. Compared to the traditional NB model, the GWPR model can better account for the spatial heterogeneity in data. Among different trip-related variables, home-based trips with the purpose of work and school by modes such as private vehicle, bike, walk to local bus, and park and ride had the most important impacts on aggregated crash data. Among roadway characteristics variables, length of freeways and major arterials were found to have significant association with total and severe crashes. The results of this study provide a better understanding of the effects of different modal shares and trip purposes on traffic safety.