The Iterative Calculation of Full Capacity of Roundabouts

The full capacity of roundabout is the maximum value of the sums of all entry flows. On the assumption that the traffic operation characteristics are remained unchanged which include critical gap, the minimum headway, the following headway and the turn-orientation proportion of each entry, the sum of all entry flows is the full capacity of roundabout when each entry flow is equal to the entry capacity correspondingly. The entry capacity can be calculated by use of the equation based on the gap acceptance theory. This process can be finished with the help of computer. This paper analyzed the difference of calculations between single-lane roundabouts and double-lane roundabouts. The full capacities are calculated using the roundabout cases in Dalian, China. The theoretical calculation value was verified and the study found that full capacity of roundabouts should be unique solution and unrelated with the initial flows of entries.