This report documents the algorithm for predicting the safety performance of rural two-lane highways that forms the basis for the Crash Prediction Module of the Interactive Highway Safety Design Model. The algorithm estimates the effect on safety performance of roadway segment parameters including lane width, shoulder width, shoulder type, horizontal curves, grades, driveway density, two-way left-turn lanes, passing lanes, and roadside design, and of intersection parameters including skew angle, traffic control, exclusive left- and right-turn lanes, sight distance, and driveways. The algorithm enables highway agencies to estimate the safety performance of existing or proposed highways and to compare the expected safety performance of geometric design alternatives.
Michael F. Trentacoste
Director, Office of Safety Research and Development
This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United States Government assumes no liability for its content or use thereof. This report does not constitute a standard, specification, or regulation.
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|1. Report No.
|2. Government Accession No.
||3. Recipient's Catalog No.
|4. Title and Subtitle
PREDICTION OF THE EXPECTED SAFETY PERFORMANCE OF RURAL TWO-LANE HIGHWAYS
|5. Report Date
|6. Performing Organization
D.W. Harwood, F.M. Council, E. Hauer, W.E. Hughes, and A. Vogt
|8. Performing Organization Report No.
|9. Performing Organization Name and Address
Midwest Research Institute
425 Volker Boulevard
Kansas City, Missouri 64110-2299
|10. Work Unit No. (TRAIS)
|11. Contract or Grant No.
|12. Sponsoring Agency Name and Address
Office of Safety Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, Virginia 22101-2296
|13. Type of Report and Period Covered
May 1997—September 2000
|14. Sponsoring Agency Code
|15. Supplementary Notes
Contracting Officer's Technical Representative (COTR): Michael S. Griffith, HRDS-06
This report presents an algorithm for predicting the safety performance of a rural two-lane highway. The accident prediction algorithm consists of base models and accident modification factors for both roadway segments and at-grade intersections on rural two-lane highways. The base models provide an estimate of the safety performance of a roadway or intersection for a set of assumed nominal or base conditions. The accident modification factors adjust the base model predictions to account for the effects on safety for roadway segments of lane width, shoulder width, shoulder type, horizontal curves, grades, driveway density, two-way left-turn lanes, passing lanes, roadside design and the effects on safety for at-grade intersections of skew angle, traffic control, exclusive left- and right-turn lanes, sight distance, and driveways.
The accident prediction algorithm is intended for application by highway agencies to estimate the safety performance of an existing or proposed roadway. The algorithm can be used to compare the anticipated safety performance of two or more geometric alternatives for a proposed highway improvement.
The accident prediction algorithm includes a calibration procedure that can be used to adapt the predicted results to the safety conditions encountered by any particular highway agency on rural two-lane highways. The algorithm also includes an Empirical Bayes procedure that can be applied to utilize the safety predictions provided by the algorithm together with actual site-specific accident history data.
|17. Key Words
Empirical Bayes Estimation
|18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, Virginia 22161.
|19. Security Classif. (of this report)
|20. Security Classif. (of this page)
|21. No. of Pages