Developing a GIS safety analysis system a case study

GIS has become one of the most used programs for various project and research areas. It has been widely used in a variety of applications for planning, presenting, and analyzing data and results. Its application in transportation safety however, has been limited. ArcGIS provides the option of creating new tools by programming with different languages such as Visual Basic. Most of the available GIS-based traffic safety tools developed so far perform simple traffic crash analyses by querying, analyzing crash data and ranking of high crash locations by using crash data only. The objectives of this study are three-fold: (1) to review and identify the most important features and methods in safety analysis; (2) to develop a safety analysis application using ArcGIS and Visual Basic; (3) to use the application in a case study. The safety application developed is able to query traffic crashes by accident characteristics which are always reported and included in any traffic accident database such as crash severity, road condition, collision type, light condition, etc. The application also performs analysis both on a micro level and on a macro level. Users have the choice of studying an intersection or a roadway segment as well as a group of intersections or roadway segments that share common characteristics or traits. Eight different safety analysis methods were programmed, which ranged from simple methods such as the crash frequency to the more advanced methods such as the empirical Bayes (EB). A before-after study tool is added and it is able to perform a naïve before-after study and an empirical Bayes study. Finally an output tool is added to the application so the results can be exported to other formats or maps. The application is tested with a case study using Montgomery County as a study area