Implementation of Highway Safety Manual Freeway Ramp Segment Calibration and the Lessons Learned

摘要

This study estimated the Highway Safety Manual (HSM) calibration factors for freeway ramp segments using Kansas data and further identified the challenges faced during the calibration effort. At the time of this study, no comprehensive study has been conducted under this research focus. The results indicated that the HSM methodology overpredicted all single vehicle crashes and multiple vehicle fatal and injury crashes resulting calibration factors 0.165, 0.368, and 0.957, respectively, and underpredicted multiple vehicle property damage only crashes resulting a calibration factor of 2.737 for entrance ramps in Kansas. Considering exit ramps, the HSM methodology underpredicted all multiple vehicle crashes resulting calibrations factors 5.426 and 7.973 and overpredicted all single vehicle crashes resulting calibration factors 0.179 and 0.550 in Kansas. The major challenge of this entire calibration was the identification of ramp crashes, where the study manually reviewed 9,720 interchange-related crash reports to locate crashes occurred on ramps.