Synthesis of Methods for Estimating Pedestrian and Bicyclist Exposure to Risk at Areawide Levels and on Specific Transportation Facilities
Source: Federal Highway Administration (FHWA)
Summarizes the variety of methods used to estimate and evaluate exposure to risk in pedestrian and bicyclist safety analyses. In the literature, the most common definition of risk was a measure of the probability of a crash to occur given exposure to potential crash events. There was also consensus on a theoretical definition of exposure as a measure of the number of potential opportunities for a crash to occur. However, there is wide divergence on operational definitions of exposure, and an even wider range of exposure measures being used in practice. Geographic scale is a critical element in most exposure analyses, and most analyses reviewed could be grouped into one of four scales: 1) regional (e.g., city, county, state); 2) network (e.g., traffic analysis zone, Census tract, Census block group); 3) road segment; and, 4) point (e.g., mid-block or intersection street crossing). This report summarizes numerous examples of exposure estimation methods at these different geographic scales, and discusses the data sources and analytic methods used to estimate exposure in these different geographic scales. Other pedestrian and bicyclist risk factors besides exposure also are cataloged.
