Observations and comparisons of maximum entry and circulating capacities at multilane roundabouts.

In this paper, the boundary capacity conditions at a multilane roundabout in Sharjah, United Arab Emirates, were directly observed at each entry and circulating lane, and the results compared with the estimated capacity from several roundabout models widely used around the world. The study roundabout has three circulating lanes and two entry lanes on each approach. From observation, the maximum entry flow was calculated to be 1818 and 1644 vehicle per hour for the left and right lanes respectively. The maximum circulating flow is 1498, 1758, and 731 vehicle per hour for the inside, middle, and outside lanes respectively. The low flow (731 vehicle per hour) on the outside circulating lane is an apparent indication of different lane utilisation. It was also found that of all the models tested, the Australian gap-acceptance model provided the best estimates for multilane roundabout maximum entry and circulating flows, and that improved capacity estimates were achieved when the gap-acceptance models used local parameter estimates. (a).