Capacity and performance of roundabouts

Abstract

Empirical and theoretical approaches for assessing the capacity and performance of roundabout entries have provided inconsistent results. It was believed that an efficient modeling of gap-acceptance behavior of drivers entering into a roundabout would provide more insight for assessing roundabout operation. Accordingly, this study used logit modeling to predict the probability that a randomly selected driver will accept a given gap in the circulating traffic stream based upon roundabout and gap characteristics. Also, the study has developed move-up time models using both the roundabout geometry and circulating traffic characteristics. The developed gap-acceptance and move-up time models have implications in roundabout capacity estimation analysis. Finally, the results of the developed models are incorporated into the Australian and German gap theoretical models to judge the feasibility of using these theoretical models for Jordan conditions. Compared with an empirical data set, the Australian theoretical model with a minimum headway of 0.5 s provides reasonable results.Key words: capacity analysis, probabilistic approach, roundabouts.