Abstract
This report presents a comparative study on some of the widely used capacity calculation procedures and recently developed models. A comparison of various capacity models for roundabouts is conducted with an independent data set. The main results and conclusions are that the gap acceptance models with fixed or constant parameter values do not provide a complete description of the processes for capacity operation. It is concluded that the move up time should be a function of the circulating flow, and that gap forcing and driver relaxation modify capacity significantly. With the average gap acceptance parameter values from the literature, the gap acceptance models predict capacities fairly well at moderate circulating flows.