Assessing the applicability of the highway safety manual to gravel roads: A case study of Wyoming

Abstract

Gravel road safety is a crucial area of road safety since gravel roads represent a substantial proportion of the entirety of the nation’s roadway network. Also, gravel roads pose inherent hazards that are otherwise absent in paved roads. Nonetheless, research related to gravel road crash count prediction models, known as safety performance functions (SPFs), was rarely undertaken. SPFs are required for identifying high crash risk locations, or hot-spots, and assessing changes in crash counts before and after implementing safety countermeasures. This research offers a diagnosis of the applicability of the Highway Safety Manual (HSM) to gravel roads in Laramie County, Wyoming. Even though the HSM does not address gravel road safety, the most appropriate methodology, provided by the HSM, for predicting counts of crashes on gravel roads is that of rural two-lane highways. This methodology is applied to Laramie County’s conditions and, as per the results, it is interpreted that the methodology is not applicable to such conditions. Therefore, developing SPFs for Wyoming’s conditions are recommended even though this involves labor hours, expertise and costs. Also, including a chapter in the HSM, devoted to gravel road safety, is suggested.