Intersection Safety Performance Function Calibration for Project Planning and Design

About the report

This study calibrated the predictive models for conventional intersections in the Highway Safety Manual (HSM) second edition draft to account for local conditions in Virginia. The calibration ensures that predictions made with the HSM safety performance functions accurately reflect the crash experience, driver population, and environmental characteristics of the state. Crash, traffic, and geometric data were collected for 1,326 intersections across Virginia, representing minor road stop-controlled, all-way stop-controlled, and signal-controlled configurations on rural two-lane, rural multilane, and urban or suburban arterial highways. The study followed HSM-recommended procedures to estimate calibration factors and dispersion parameters for the conventional intersection site-type safety performance functions in the HSM second edition draft.

Constant calibration factors provided a good fit for total crashes, with 20 of 21 site types meeting HSM acceptance criteria, but they did not perform as well for fatal and injury crashes. Calibration functions offered a superior fit for those crash types, with 14 of 19 site types achieving percent cumulative residual deviations within 5%. It is recommended that the Virginia Department of Transportation Traffic Operations Division use the constant calibration factors in Table 11 for total crashes and the calibration functions in Table 12 for fatal and injury crashes and incorporate these results into the Traffic Operations and Safety Analysis Manual to ensure consistent statewide application.

_{Disclaimer Statement:The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.}

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