Collision diagrams, which are graphical representations of accident experience at intersections or along roadway segments, are an integral part of the analysis of hazardous roadway locations. Historically, collision diagrams have been prepared manually by a laborious search of accident files, organization of selected accident reports, and manual preparation of diagrams. Since the development of computerized accident data systems and computer graphics hardware, several software systems have been developed to prepare collision diagrams. Although a number of these efforts have not been reported, the ones that have are generally schematic in nature. Some procedures involve presenting groups of accidents, by type, by means of a single symbol. Presentation of a group of similar accidents at one location sometimes lacks visual impact, and visual impact is one of the most important features of the use of collision diagrams in accident analysis. The development of an automated system to produce collision diagrams that represent each accident by a single symbol is reported. The automated collision diagram system uses existing computer-based accident files directly, is easy and cost effective to use, and produces a high-quality collision diagram.