The effect of lane utilization on the capacity of multi-lane traffic roundabout

Capacity of traffic roundabout is typically captured by the entry capacities of individual approaches while considering the effects of conflicting flows. Moreover, capacity of multi-lane roundabout is conventionally evaluated through a flow aggregation methodology. Multi-lane roundabout is there of treated similarly to a single-lane roundabout but of a larger size. This paper analyzes the effect of lane utilization on the capacity of multi-lane roundabout. Through a flow separation methodology, entry capacity is determined for each entry lane rather than aggregated for each approach. Kimber's formulae for entry capacity are adopted for this analysis. The results show that capacity estimated by flow separation could be considerably lower than that by aggregation method. Moreover, the flow balance among circulating lanes plays an important role in the roundabout performance.