Reliability, Flexibility, and Environmental Impact of Alternative Objective Functions for Arterial Offset Optimization

Abstract

A wide variety of alternative optimization objective functions, such as minimizing stops, minimizing delay, and maximizing arrivals on green, has been reported in the literature. An extensive literature evaluates these alternative objective functions with models. This paper reports on the field deployment of these alternative optimization functions, developed with high resolution controller data, to adjust offsets on an arterial system of eight coordinated signals. The deployment consisted of a 1-week base data collection and four 1-week deployments of offset plans developed with four alternative optimization objective functions. Travel times of anonymous probe vehicles were measured during the study period to evaluate the impact of these alternative optimization functions on corridor travel time. All objective functions were successful in reducing median corridor travel time significantly. Median travel time decreased by more than 1 min in both directions on the 5-mi corridor. Travel time reliability, as quantified by the difference between 75th and 25th percentile travel times, was improved for the busiest portion of the day. A lower bound of the estimated annual savings on user costs was $472,817, with an associated reduction in carbon dioxide emissions of 197 tons per year.