Measuring the spatiotemporal evolution of accident hot spots

One reality of transportation systems is that vehicular accidents can happen practically anywhere and at any time. An increasing body of research suggests though that spatial and/or temporal dependencies (i.e., clusters or hot spots) among accidents likely exist. Along with understanding where and when such spatiotemporal dependencies may occur, another important facet to consider is the geographic extent or area associated with the hot spots. For example, an accident hot spot may involve a small, isolated portion of the transportation system or a much more expansive geographic area. Better delineation and quantification of the morphological characteristics of accident hotspots can provide valuable decision support for planning for accident hot spot mitigation and prevention. As the size and shape of accident hot spots may evolve over time, the capability to track such dynamics is vital, especially with respect to the identification of processes effecting hot spot occurrence as well as assessments of the efficacy of efforts to mitigate factors underlying hot spot development. To this end, a Geographical Information Systems (GIS) based framework is outlined to facilitate the analysis of the morphological characteristics of hot spots over time. The analysis framework is applied to a case study of vehicular accidents reported over a two-year period to demonstrate its practical utility. The application results indicate that patterns of change in hot spot morphology can be effectively quantified and a variety of informative spatial and temporal patterns can be detected.