Geographic Information Systems: Unique Analytic Capabilities for the Traffic Safety Community

Geographic information systems (GIS) have been used for more than a decade to display crash sites. Now that their novelty has worn off, the traffic records community should ask what additional analytical benefits GIS can uniquely provide. A literature review illustrates that safety-related GIS analytical capabilities surpass the common practice of producing crash location pin maps. Additional useful GIS techniques include using grid-based modeling; producing increasingly accurate collision diagrams; verifying disparate sources of crash data; applying spatially based statistical applications; examining crash location patterns for causal factors; aligning public opinion with real data; and improving routing capabilities for pedestrians, bicyclists, and hazardous material carriers. This research explores GIS analytic capabilities that can be practically applied to crash data evaluation. A case study demonstrates that despite limited budgets and imperfect data, GIS can still help to identify potential crash countermeasures. Using a typical non-GIS source of crash data (a software package that records crashes at either an intersection or a midblock location), it was possible to place approximately 82 percent of crash locations within a GIS. When private property crashes were excluded from this process, the placement rate climbed to an estimated 94 percent for intersections and 87 percent for midblock locations. By focusing the case study on understanding the practical spatial analytical capabilities rather than merely the mechanics of specific GIS software, one can eventually take advantage of the more extensive crash and roadway data sets that will become available. Despite its many capabilities, however, GIS has not eliminated the need for a comprehensive safety analysis framework integrating the spatial and statistical queries necessary for engineering, enforcement, or educational improvements.