Evaluation of Cost-Effective Alternative Designs for Rural Expressway Intersections

US Transportation Collection2021PDFTech ReportMolan, Amirarsalan MeharaHoward, JonathanIslam, Mouyid BinPande, AnuragCalifornia Polytechnic State University, San Luis Obispo. College of Engineering. Department of Civil & Environmental EngineeringSan Luis Obispo Council of GovernmentsCenter for Transportation, Equity, Decisions & Dollars (CTEDD). University of TexasUnited States. Department of Transportation. University Transportation Centers (UTC) ProgramCenter for Transportation, Equity, Decisions and Dollars (CTEDD)CaliforniaUnited StatesAlternatives analysisBefore and after studiesCost effectivenessExpresswaysHighway designHighway safetyIntersectionsRural highwaysU turnsCOVID-19Surrogate measuresR-CUTJ-turnCTEDD 019-08USDOT -69A3551747134Final ReportDespite numerous studies demonstrating the effectiveness of Restricted Crossing U-Turn (RCUT) intersection design, its implementation remains uneven and close to zero in some large states, including California. This research provides a comprehensive framework to estimate the operational and safety performance of future RCUT designs in California. The framework is demonstrated for five intersections located on high-speed rural expressways in Caltrans districts 5 and 6. The operational evaluation relies on microscopic simulation models of existing two-way stop control (TWSC) and alternate RCUT designs used to estimate network-wide performance measures. Two approaches were demonstrated for future safety estimation; first, an HSM-prescribed Empirical Bayes approach that uses Safety Performance Function (SPF) predictions combined with the crash history of the site. For typical applications, Empirical Bayes estimates may be combined with CMFs for RCUT found in the literature. This approach remains the preferred option for safety estimation. However, for geometrically constrained locations where atypical RCUT designs need to be evaluated, a surrogate measure-based method that uses trajectory data from the simulation model is described. The framework demonstrated here may be used by agencies to estimate the future benefits of the first-time application of treatments that have been successful elsewhere. Based on the results, a reduction of the number of high-severity (fatal and injury) crashes is expected by constructing an RCUT intersection; however, the number of low-severity (no injury) crashes might be increased. Regarding traffic operation, no significant difference was identified between RCUT designs and the existing intersection designs at four of the five intersections evaluated. One of the intersections did result in travel time savings due to moderately high left-turn traffic from the minor road.120