Safety Evaluations for Skewed Intersections on Low-Volume Roads: Case Study

Document Type


Publication Date



Safety on low-volume roads is a major concern. It has been reported that the traffic fatality rate is more than three times higher on rural roads than on other roads. Some of these fatalities occur at inter sections, and the safety risks increase when the intersections are skewed or have an elevation difference. In Idaho, some skewed intersections (e.g., those on SH-39 and US-91 in eastern Idaho) are the result of highways having been built parallel to rivers or railroad lines and local roads having been built later on a grid with a north–south or east–west orientation. In an attempt to improve the safety of existing intersections, the Idaho Transportation Department's District 5 performed a systematic and comprehensive evaluation of all of the intersections on the state highway system in southeastern Idaho. In total, 125 intersections along US-91 and 194 intersections along SH-39 were evaluated, and safety improvements were made. These improvements resulted in a reduction in the overall number of crashes along these two highways. This paper presents the results of these evaluations and the recommendations that followed.