Multiobjective Evaluation in Countermeasure Selection at Two-Way Stop-Controlled Intersections: Considering Traffic Operation, Safety, and Environment

Abstract

This study developed a procedure to conduct multiobjective evaluations in the traffic countermeasure (CM) selection process at two-way stop-controlled (TWSC) intersections. The economic benefits of three vehicle safety–related CMs were calculated considering not only safety impacts, but also operational and environmental impacts. First, for each CM, VISSIM simulation models were developed to obtain the average delay, vehicle emissions, and fuel consumption for the intersection before and after the treatment. The traffic operational impacts were calculated as the change in delay costs. The environmental impacts were calculated as the change in vehicle emissions and fuel consumption costs. Next, safety performance functions and crash modification factors were used to calculate the safety impacts as the crash reduction benefits for various CMs. Finally, the life-cycle cost method was used to combine the different components into the total benefit. The Monte Carlo simulation method was used to conduct uncertainty analysis through random sampling from probability descriptions of uncertain input variables to generate a probabilistic description of results. The findings showed, first, that the operational and environmental impacts accounted for a large proportion of the total impacts, which can significantly affect the selection of CMs. Second, the rankings of the CMs differ depending on whether the safety impacts alone are considered or different impacts are considered together. The study illustrates the detailed process of evaluating projects considering multiple objectives. The findings also explain how different objectives can have countervailing effects in improving motorist safety at TWSC intersections.