Phase diagram of a single lane roundabout

Using the cellular automata model, we numerically study the traffic dynamic in a single lane roundabout system of four entry/exit points. The boundaries are controlled by the injecting rates alpha(1), alpha(2) and the extracting rate beta. Both the system with and without Splitter Islands of width L-sp are considered. The phase diagram in the (alpha(1), beta) space and its variation with the roundabout size, P-agg (i.e. the probability of aggressive entry), and P-exit (i.e. the probability of preferential exit) are constructed. The results show that the phase diagram in both cases consists of three phases: free flow, congested and jammed. However, as L-sp increases the free flow phase enlarges while the congested and jammed ones shrink. On the other hand, the short sized roundabout shows better performance in the free flow phase while the large one is more optimal in the congested phase. The density profiles are also investigated. (C) 2016 Elsevier B.V. All rights reserved.