Roundabouts have long been a staple as an intersection configuration in the United Kingdom and elsewhere in Europe. Although they have been present in limited numbers in North America, they have only recently been a subject of interest in Ontario. Roundabouts can provide increased safety and reduced delay to road users under suitable circumstances. The Ontario Ministry of Transportation has initiated a variety of activities aimed at the investigation of roundabouts as an alternative to signalized intersections in appropriate locations. One such activity is the selection of a suitable method or methods for evaluating the operational performance of roundabouts. A variety of methods are available, ranging from analytical/empirical to simulation. This paper reports on initial investigations to compare the efficacy of six methods, based on their performance with respect to level-of-service evaluation at several case-study roundabouts. It was apparent that all methods reasonably estimated delay at lower volume levels. Unfortunately, the available data did not cover situations close to or at capacity levels sufficiently well to arrive at a definitive conclusion under those conditions. However, it was apparent that the results from the various methods demonstrated increasing variability with increasing traffic levels. Based on the evaluation reported here, a provisional strategy has been proposed for the operational evaluation of roundabouts in Ontario. However, further evaluation is required in conjunction with additional data collection under congested conditions to confirm the proposed strategy. (A) For the covering abstract of this conference see ITRD number E220308.
Abstract