Calibration of the Louisiana Highway Safety Manual
Bridget Robicheaux and Brian Wolshon, February 2015
The application of the American Association of State Highway and Transportation Officials’ (AASHTO) Highway Safety Manual (HSM) to Louisiana roads is a key component to the Louisiana Department of Transportation and Development’s (DOTD) plan to improve safety on state highways and reach the goal of Destination Zero Deaths. The goal of this project was to develop Louisiana state-specific HSM calibration factors for eight facility types. During the completion of the project, the data-intensive computational process undertaken to compute the calibration factors revealed numerous issues associated with the input data required by the HSM. These included, most notably, coding errors and missing required data elements in the Louisiana roadway and crash databases. Some of the resulting factors were unexpected, in particular, those for urban three lane and urban five lane highways which were lower than anticipated. These factors may warrant further analysis beyond which was required for this project, including detailed assessments of each crash report to ensure data accuracy. The remaining calibration factors for rural two lane, rural multilane undivided and divided, urban/suburban two lane, and urban/suburban four lane divided and undivided highways, ranged from a low of 0.62 for rural multilane undivided highways to a high of 2.54 for urban/suburban four lane divided highways. It is expected that with an understanding of the conditions under which these factors were developed, that they will be acceptable for use by analysts seeking to conduct highway safety analyses for roads in Louisiana.
Keywords: Highway Safety Manual, Calibration, Crash, Crash Modification Factor, Safety Performance Function
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