Research Article Transportation Research Record 1–9 Ó National Academy of Sciences: Transportation Research Board 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0361198119853549 journals.sagepub.com/home/trr Identifying Candidate Locations for Safety Improvements on Low-Volume Rural Roads: The Oregon Experience Ahmed Al-Kaisy 1 , Levi Ewan 1 , and Fahmid Hossain 1 Abstract Low-volume roads constitute a significant proportion of the roadway network in rural areas, but they are usually associated with sparse crash data. This makes it impractical to rely on crash history alone to identify candidate locations for more detailed safety investigations and potential improvements. This paper presents the development of a prioritization scheme, in the form of a crash risk index, to be used in ranking candidate sites for safety improvements on low-volume roads in the State of Oregon. The index developed utilizes information on highway geometry, roadside features, traffic exposure, and crash occurrence in assessing risk, rather than relying solely on crash history in identifying hazardous locations. A roadway sample with a total length of around 830mi was used in this study to represent different geographic regions in the state. Subsequently, extensive roadway, traffic, and safety data for the study sample were acquired and utilized in the development of the proposed index. A case study application of the proposed crash risk index on a 16-mi low-volume road corridor is presented which shows how to apply the index practically on a typical low-volume road using information readily accessible to the agency. Maintaining safety on the roadway system has become the utmost priority for most highway agencies in recent years. Traffic crashes and associated casualties remain at alarming levels in the United States, which has led all states to work relentlessly in finding various ways to improve road user safety within their jurisdictions. However, highway agencies have been facing increas- ingly tight budgets, including for funds dedicated to their ongoing safety programs. Therefore, it is essential for highway agencies to be able to identify those loca- tions that are associated with higher crash risks for optimum use of their limited resources. Reliable assess- ment of risk on the highway system is critical in the process of identifying those sites that are in need of safety improvements. This paper presents the results of a study sponsored by the Oregon Department of Transportation (ODOT) to develop a systematic methodology for ranking sites that are in need of safety improvements on low-volume rural roads. A crash risk index has been developed which is intended to assess risk on roadway segments at the net- work level using roadway geometry, roadside features, traffic exposure, and crash history. The following sec- tions in this paper will summarize the development of the crash risk index along with a case study application of the proposed methodology. The Challenge of Assessing Risk on Low-Volume Roads Crashes are random events and consequently can occur at any location along the roadway. On roadways with higher traffic volumes, the more frequent occurrence of crashes allows for the direct identification of high crash locations using historical data. However, on low-volume roads, which constitute an extensive network of the high- way system, crash occurrence, particularly fatal and seri- ous injury crashes, is less frequent. This makes it difficult to identify trends and treat hazardous sites based on his- torical crash data. Traditional methods for identifying candidate locations for safety improvements are inher- ently biased in favor of well-traveled roadways which experience higher crash frequencies. However, low- volume roads may be associated with higher level of risks and consequently higher crash rates. Moreover, low- volume roads are often built to lower geometric and roadside standards (given their functional class), which constitutes an added risk to road users, yet above-normal 1 Western Transportation Institute, Montana State University, Bozeman, MT Corresponding Author: Address correspondence to Ahmed Al-Kaisy: alkaisy@montana.edu