Abstract
The United States Road Assessment Program (usRAP) provides a systemic approach to estimate the risk of severe injury and fatal crashes along roadway segments based on the expected safety performance of roadway and roadside characteristics, together with a general estimation of traffic volume. Detailed crash data are not needed for safety assessments, providing advantages over more traditional crash-driven approaches. However, experiences with usRAP are limited to the United States and to date, the program has a growing but limited number of participating states. Verification of the adequacy of usRAP assessments is therefore of significant value, not only to identify strengths and limitations of the methodology within the U.S. context, but also to potentially expand the set of tools available to agencies. This paper presents a verification of usRAP risk assessments for run-off-road and head-on crashes using over 7,000 mi of coded segments and five years of crash data collected in Utah. Comparisons between risk estimations from usRAP and actual crash rates provided insights into the expected and observed effects of roadside objects and their distances from the lanes traveled, type of median present, and horizontal curves. A spatial correlation test also confirmed the agreement between usRAP risk assessments and crash data, providing additional promising indications of the suitability of this systemic methodology for safety applications.
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