Calibration of Safety Performance Functions for Freeway Ramp Terminals in Virginia

Chapter 19 of the Highway Safety Manual (HSM) provides safety performance functions (SPFs) for freeway ramps and crossroad terminals. The chapter includes more than 100 predictive models for ramp terminals characterized by site type, intersection control, crash severity, area type, and number of crossroad lanes. These SPFs need to be calibrated to Virginia conditions to ensure that they accurately reflect the driver population and environment. The application of uncalibrated SPFs may produce misleading results, compromise safety outcomes, and lead to inappropriate design decisions. The purpose of this project is to conduct systematic calibration of the HSM ramp terminal SPFs to account for conditions in Virginia. This involves aligning the expected average crash frequencies estimated using HSM methodologies with field-observed crash frequencies from selected sites.