Agent-based modeling of lane discipline in heterogeneous traffic

Designating lanes for different vehicle types is ideal road safety-wise. Practical considerations, however, require road sharing. Using a modified Nagel–Schreckenberg cellular automata model for two vehicle types (cars and motorcycles), we analyzed the interplay of lane discipline, lane changing, and vehicle density. In the absence of lane changing, the transition between free flow and congested states occurs at a higher vehicle (road occupation) density when the ratio of cars to motorcycles is increased. When lane changing is allowed, the smaller motorcycles tend to fill in unused spaces, until the point when the wider cars effectively block their way at high vehicle densities. When the condition of lane discipline is not imposed, i.e. staying wholly within lane boundaries is not required, further improvement in throughput becomes possible at the cost of required driver attentiveness. •A modified Nagel–Schreckenberg model for heterogeneous traffic is proposed.•Phase transition, from free flow to congested flow, depends on vehicle length.•Lane change can benefit narrow vehicles, and is undesirable for wide vehicles.•Lane discipline breakdown may improve throughput at the cost of safety.•A simple collision index is proposed.