Assessment of statewide intersection safety performance.

SPR 667This report summarizes the results of an analysis of the safety performance of Oregon\u2019s intersections. Following a pilotstudy, a database of 500 intersections randomly sampled from around the state of Oregon in both urban and ruralenvironments was assembled. These intersections were categorized into eight types based on number of legs (3 and 4),land use (urban or rural) and traffic control (signalized or minor stop-control). These categories were chosen to align withthe intersection types in AASHTO\u2019s recently released Highway Safety Manual (HSM). Geometric and traffic controlelements were supplemented by compiling crash data and volumes on the major and minor approaches. The safetyperformance was analyzed by three primary methods. First, crash rates were calculated and analyzed for each of theintersection groups. Crash rates determined for Oregon intersections were generally well below rates found published forother states. Since it is unlikely that such a significant difference exists in the safety performance between states, it ismore likely explanation is the different reporting thresholds and Oregon\u2019s reliance on self-reporting. Second, crashpatterns were tabulated for a number of crash and driver involved variables. These patterns, not before generated, will bevery useful to improve identification of high crash intersection locations and improve diagnosis of these locations. Third,safety performance functions (SPFs) were created for intersections where sufficient data exist. For the purposes of thisresearch SPFs were estimated for the rural 3-leg stop controlled and urban 4-leg signalized intersections. The SPFsdeveloped in this modeling exercise were compared to the HSM base models calibrated to Oregon. The rural 3-leg stopmodels compare favorably. Within the volume range of the data used to generate the SPFs, the models compare well. Theurban signalized intersection SPFs did not compare as well to the HSM base models. Further research is needed toinvestigate whether Oregon-specific SPFs have advantages over calibrated HSM models. The results of this analysis canbe used to improve the diagnosis and identification of unusual safety performance at intersections in Oregon. The averagerates are useful for peer comparisons and in calculation of critical rates. The crash patterns can be directly applied indiagnostic efforts to detect unusual patterns at intersections. The SPF modeling effort is the groundwork for furtherexplorations and model development for Oregon facilities