Turboroundabouts Along Corridors: Analysis of Operational and Environmental Impacts

Abstract

The number of turbo-roundabouts constructed in Europe has grown steadily in the past decade. While there has been extensive work on the operational and environmental impacts of isolated turbo-roundabouts, research on closely-spaced turbo-roundabouts along corridors is somewhat lacking.The objective of this research is to evaluate the impact of turbo-roundabout corridors on both traffic performance and emissions. The research has three major thrusts: 1) to identify the hotspot emission locations along turbo-roundabout corridors; 2) to compare the overall performance of turbo-roundabout corridors against conventional two-lane roundabouts on arterials; 3) to address the integrated effect of geometric and operational characteristics of turboroundabout corridors on carbon dioxide, carbon monoxide, nitrogen oxides and hydrocarbons emissions.Vehicle activity along with traffic flow data were collected from three turbo-roundabout corridors in the Netherlands. Site-specific operations were analyzed using microscopic traffic and emissions platforms (respectively, VISSIM and Vehicle Specific Power -VSP).The results showed that emission hotspots along these corridors occurred in the segments located just downstream of the turbo-roundabout, both in absolute terms (more than 30% of total emissions) and per unit distance. It was also found that the implementation of two-lane roundabout corridors outperformed the turbo-roundabout corridors in terms of vehicle emissions, however the differences were not statistically significant (p-value<0.05). Data analysis indicated that an additional decrease in corridor's emissions (4-11%, depending on the pollutant) may be reached by altering the spacing (from 180 to 240 m) between two-closely spaced turboroundabouts.

Assessing the Environmental Performances of Urban Roundabouts Using the VSP Methodology and AIMSUN

“…Thus, more experience should be carried out both to generalize the results and to test the transferability of the proposed methodology into other environmental contexts. In other case studies, operational and environmental impacts of turbo-roundabouts were also analysed both as isolated intersections [48,49] and along corridors [50]. Improvements in the estimates of CO 2 emissions and fuel consumption on arterial roads have been achieved coupling dynamic micro traffic models with instantaneous emissions models; however, the large computation times especially for large-scale urban networks is a drawback of this kind of combination [51].…”