Performance Evaluation of Basic Turbo Roundabouts as an Alternative to Conventional Double-Lane Roundabouts

Abstract

Since their introduction in the late 1990s, basic turbo roundabouts have made a great success in several European countries. Researchers, however, have been unable to reach a general consensus on the operational performance advantages and benefits derived from such a novel design of multi-lane roundabouts, as compared with conventional double-lane roundabouts. Those contradictory results could be mostly attributed to wide variations in driver behavior among different traffic environments. This study aims to analyze and evaluate the operational performance of an existing, congested double-lane roundabout in the State of Florida and a proposed, simulated basic turbo roundabout. Local field data was used to accurately calibrate and validate the microsimulation models and to precisely capture local driving behavior. Three scenarios were created for evaluation. Results indicated that basic turbo roundabouts with regulatory entry speed as per Dutch standards, that is, 25 mph, were the most suitable alternative to reduce average delay and provide comparable capacity to double-lane conventional roundabouts for traffic flow ranging between 4,350 and 6,050 vehicles per hour. However, double-lane conventional roundabouts, including their major and minor approaches, always managed to process significantly more vehicles.