Evaluation of Effectiveness of Coordinated Signal Control in Reducing Vehicle Emissions during Peak Hours versus Nonpeak Hours

Traffic signal coordination is not only an effective traffic flow operational strategy to smooth the traffic in urban areas but is also considered a potentially effective means to reduce vehicle emissions. Nevertheless, when traffic flow speed decreases, the effectiveness of using traffic signal coordination to reduce emissions may be substantially weakened. This paper evaluates the effectiveness of signal coordination in reducing vehicle emissions during peak versus nonpeak hours, two speed scenarios. The operating mode binning approach is used as a statistical technique to calculate emission rates, and the difference in emissions is adopted as the measure of effectiveness in the study. Data used in the study include Global Positioning System data and emission data collected from real-world tests. It was found from the study that coordinated signal control could reduce vehicle emissions in the following order (most to least reduction): oxides of nitrogen, carbon dioxide, hydrocarbons, and carbon monoxide. However, its effectiveness would be impaired during peak hours when the speed was decreased. Meanwhile, the test shows that the effectiveness will be affected by driver behavior. Either low average speed or intentionally slow driving will weaken the effectiveness of coordinated control in reducing vehicle emissions. The research in this paper is a pilot study and the same methodology will be used to conduct a more thorough study.