A section of KY 30 in Jackson and Owsley Counties is targeted for redesign to provide a safer and more efficient corridor that will support economic activity in eastern Kentucky. Data for the existing KY 30 alignment and eight alternative alignments developed by HMB Professional Engineers Inc. were provided to researchers at the Kentucky Transportation Center (KTC). KTC researchers also developed a new alternative that modified the existing alignment to improve the safety of various locations. Researchers applied safety analysis procedures from Part C of the Highway Safety Manual (HSM) to the existing and alternative alignments of KY 30 using the Interactive Highway Safety Design Model (IHSDM). The resulting crash predictions were used to analyze each alternative and perform a benefit-cost analysis.

Each alignment’s safety benefits were derived by calculating the total reduction in crashes (i.e., subtracting the number of crashes anticipated for an alternative from the number of crashes that would be expected if the segment were not redesigned). Comprehensive crash costs from the National Safety Council (NSC) were applied to the reduction in crashes to estimate, in monetary terms, the safety benefit. This figure was compared to the estimated cost of each project. KTC’s modified existing alignment had a benefit-cost (B/C) ratio of 0.14, meaning project’s cost outweighs the expected safety benefits. The other new build alternatives had negative B/C ratios, meaning the cost of crashes is expected to increase after their implementation. The increase in crash costs for the new build alternatives is due to the increase in crash severity expected on the new alignments coupled with the current alignment remaining a source of crashes (as the latter would remain open to facilitate the mobility of residents). IHSDM analysis only captures expected safety benefits, however. The selected alternative may be economically justifiable based on a holistic evaluation of the potential benefits it offers — in addition to safety benefits. The potential non-safety benefits of each project alternative should be analyzed to inform and improve the decision-making process for the KY 30 redesign.

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© 2017 University of Kentucky, Kentucky Transportation Center

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