Turboroundabouts Along Corridors

The number of turboroundabouts constructed in Europe has grown steadily in the past decade. Although there has been extensive work on the operational and environmental impacts of isolated turboroundabouts, research on closely spaced turboroundabouts along corridors is somewhat lacking. The objective of this study was to evaluate the impact of turboroundabout corridors on both traffic performance and emissions. This research had three major thrusts: (a) to identify the hot spot emission locations along turboroundabout corridors, (b) to compare the overall performance of turboroundabout corridors against that of conventional two-lane roundabouts on arterials, and (c) to address the integrated effect of geometric and operational characteristics of turboroundabout corridors on emissions of carbon dioxide, carbon monoxide, nitrogen oxides, and hydrocarbons. Vehicle activity along with traffic flow data was collected from three turboroundabout corridors in the Netherlands. Site-specific operations were analyzed with microscopic traffic and emissions platforms (Vissim and vehicle specific power, respectively). The results showed that emissions hot spots along these corridors occurred in the segments located just downstream of the turboroundabout, both in absolute terms (more than 30% of total emissions) and per unit of distance. It was also found that the implementation of two-lane roundabout corridors outperformed the turboroundabout corridors in terms of vehicle emissions; however, the differences were not statistically significant (p-value < .05). Data analysis indicated that an additional decrease in a corridor’s emissions—4% to 11%, depending on the pollutant—may be reached by altering the spacing (from 180 to 240 m) between two closely spaced turboroundabouts.