Lane Use and Speed-Flow Relationship on Basic Segments of Multilane Motorways in Japan

This study is aimed at analyzing and modeling the lane distribution of traffic flow and the speed-flow relationships in individual lanes for unsaturated flow on basic segments of multilane intercity motorways in Japan. The effects of rainfall and heavy vehicles are considered in all the analyses. The lane distribution model is used to assign traffic demand, which is generally given as a directional total flow, to each lane. In particular, lane-use characteristics by vehicle type are studied, so that the flow and the ratio of flow of a vehicle type in a lane can be estimated and applied to the speed-flow relationship when the traffic demand is given by vehicle type. Road geometric conditions are not taken into account. However, traffic data of 641 sites are used for the models for each case of posted speed limit and number of lanes. Thus, the models can be used for estimating average tendencies of lane-use characteristics and speed-flow relationships in individual lanes expected on a homogeneous segment. Also, the relationship between directional average speed and total flow in one direction is demonstrated using the models proposed in this study.