A Two-Dimensional BML Model of Traffic Flow Considering Overpass Configuration

Considering the widely existed grade separations in the two-dimensional urban road network, this paper incorporates some overpass configurations into the classic Biham-Middleton-Levine (BML) model, which has not yet been fully investigated. With the change of the overpass's quantity and its configuration, the effect of overpass on the network performance is discussed based on the extended BML model. Using the numerical simulation, it is found that overpass newly built but without deliberate and reasonable plan, could only aggravate the existing congestion conditions, if the overpass ratio is low. Furthermore, the configurations of grouped overpass, which could reflect the realistic characteristics of overpass distribution in the road network, such as squared and loop-shaped configurations, are incorporated into the network. It is found that the squared configuration would bring positive effects on the network flow, while loop-shaped configuration bring negative effects on the network flow under certain conditions. The simulation results overthrow the conventional perception and have the extensive applicability and practical significance.