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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.

Title:

Continuous Friction Measurement Equipment As a Tool for Improving Crash Rate Prediction: A Pilot Study
Authors:
Edgar de León Izeppi, Samer W. Katicha, Gerardo W. Flintsch, Ross McCarthy
Kevin K. McGhee
Kevin K. McGhee
Year: 2016
VTRC No.: 16-R8
Abstract: A comprehensive pavement management system includes a Pavement Friction Management Program (PFMP) to ensure pavement surfaces are designed, constructed, and maintained to minimize friction-related crashes in a cost-effective manner. The Federal Highway Administration’s (FHWA) Technical Advisory 5040.38 on Pavement Friction Management supersedes a previous advisory that focused on skid crash reduction. In addition to traditional locked-wheel friction-testing devices, this new advisory recommends continuous friction measuring equipment (CFME) as an appropriate method for evaluating pavements.

The study described in this report developed a pavement friction inventory for a single construction district in Virginia using the Grip Tester, a low-cost CFME. The continuous friction data were then coupled with crash records to develop a strategy for network analysis that could use friction to improve the ability to predict crash rates.

The crash rate analysis applied the well-established methodology suggested by the FHWA for the identification of high crash risk areas using safety performance functions (SPFs), which include empirical Bayes rate estimation from observed crashes. The current Virginia Department of Transportation SPF models were modified to include skid resistance and radius of curvature (interstate and primary system only) to improve the predictive power of the models. A variation of the same methodology was also used to contrast the effect of two different friction repair treatments, i.e., conventional asphalt overlay and high friction surface treatments, to explore how their strategic use can impact network level crash rates. The result suggests significant crash reductions with comprehensive economic savings of $100 million or more when applied to a single relatively rural district.

These findings easily justify an aggressive state-level PFMP and further support continued research to quantify the influence of other pavement-related characteristics such as macrotexture, grade, and cross-slope.