Group control of traffic at roundabouts

The paper presents the application of the group traffic control methodology to signal controlled roundabouts. This methodology is based on the group model of traffic in street network. There are three types of elements in the model: groups of vehicles, road segments and control signals. Interactions among vehicle groups and the influence of signal or road on their movement are described by the set of seven elementary transformations. In this framework the optimal cycle time and offsets are derived for four-arm roundabout excluding the blocking back effect from circulating carriageway. The new method was proved to be very efficient in stops, delay and capacity on two roundabouts in Poznan