Traffic Signal Coordination Across Jurisdictional Boundaries: Field Evaluation of Efficiency, Energy, Environmental, and Safety Impacts

Abstract

Some insight into the potential benefits of coordinating traffic signals across jurisdictional boundaries by using as a case study the Scottsdale Road–Rural Road corridor in the Arizona cities of Tempe and Scottsdale is provided. In particular, the feasibility of using second-by-second speed measurements from Global Positioning System-equipped vehicles for evaluation of the environmental and safety impacts of operational-level traffic improvement projects is demonstrated. The use of statistical models for the evaluation of efficiency, energy, emissions, and safety benefits of operational-level traffic improvement projects without the need to invest in expensive equipment such as emissions analyzers is also demonstrated. Furthermore, it is also shown that the use of statistical models allows evaluation of measures of effectiveness that would not otherwise be evaluated, such as accident risk. On the basis of a field evaluation of the main travel corridor of the study area, it was determined that the signal coordination project would increase the average speed on the main line by 6 percent over the a.m. peak, midday, and p.m. peak analysis periods. It was also found that the number of vehicle stops would be reduced by 3.6 percent, on average, whereas the fuel consumption would be reduced by 1.6 percent. The emissions of hydrocarbons and oxides of nitrogen remained constant, whereas the carbon monoxide emissions increased by 1.2 percent. Finally, the crash risk was reduced by 6.7 percent. The results for the three analysis periods indicated statistically significant benefits to the approaches of the retimed traffic signals. However, these benefits were found to be statistically insignificant when the 21 traffic signals of the entire main line were considered.