Calibrating the Highway Safety Manual Predictive Models for Oregon State Highways

摘要

The recently released Highway Safety Manual (HSM), published by the American Association ofState Highway and Transportation Officials (AASHTO), provides a comprehensive set of toolsfor evaluating and identifying opportunities to improve safety for highway facilities. Included inthe HSM is a quantitative method for predicting crashes based on recently developed scientificapproaches. These predictive methods currently exist for three specific facility types: rural twolaneroads; rural multilane highways; and urban and suburban arterial highways. To enhanceprecision, each HSM predictive method should be calibrated for location conditions. This paperdemonstrates the HSM calibration procedure for total crashes in Oregon. The research identifiedthree critical data collection issues including information about pedestrian volumes, minor roadtraffic volumes at rural locations, and minimum sample size for under-represented crashlocations. The authors also determined that most of the calibration factors for Oregon areconsiderably lower than expected values of approximately one and attributed this observation toOregon crash reporting thresholds and procedures. The paper also includes an evaluation of crashseverity distribution methods as well as assesses the significance of collision type distributionson the overall predicted crashes.