Capacity of Mini-Roundabouts: A New Model

Estimation of the capacity of mini-roundabouts is under discussion. Existing methods treat mini-roundabouts as analogous to larger roundabouts, assuming independence between operation of the entries. They fail to acknowledge the specific way that traffic operates at these narrow intersections. This study proposed a new model, which aimed to accommodate the peculiarities of mini-roundabouts: priority for upstream entry, capacity increasing effects of exiting vehicles, and heavy vehicle operation. The model resulted in a set of equations that can be solved iteratively. It was applied to a set of examples in which the model parameters were estimated according to existing guidelines. Test calculations showed: compared to the current German guidelines the model leads to a reduced total intersection capacity. Further calibration and tests for practicability are recommended.