Effect of roundabout operations on pollutant emissions

This research quantifies the traffic and emission impacts of single lane roundabouts in urban corridors, based on experimental measurements of traffic and using the “Vehicle Specific Power” emission estimation methodology. Experimental data were gathered from single lane roundabouts located in Lisbon (Portugal) and Raleigh (US). Using congestion-specific vehicle speed profiles on the roundabout approaches, the emissions calculation methodology is able to quantify the relationships between vehicle dynamics and emissions. The main contributions are: the characterization of a limited set of synthetic speed profiles that occur at a roundabout approach, the frequency distribution of these profiles based on congestion levels, and the correlation between queue length and the number of stop and go cycles. Two different types of stop and go driving cycles for vehicles joining the queue at a roundabout were identified: short and long.