Modeling Vehicles Movement at Signalized Intersections

Behaviors of car following at signalized intersections are different to those on roads, especially during the start part of green time. As green indication starting, vehicles in the linked approach begins to move and often emerges a particular course observed as that a closely-spaced platoon of moving vehicles comes into being and then turns to disperse. This course usually takes place for the interrupted flows, especially for the resting queues, during the early period of their re-moving. This paper divides movement of each vehicle in this course into four stages: initially accelerating from rest, shortly after which reducing acceleration rate to join a moving platoon, then increasing acceleration rate to disperse from the platoon and eventually stepping into a free flow. It develops a mathematic model to describe the four-stage movement. It also designs a performance measure (intersection passing time) and carries out some case studies based on field data in Beijing city to validate the model. It reveals that the proposed model is applicable to model vehicles movement during the start part of green time. It is found by the proposed model that drivers' decisions at the second stage have much effect on total delay of vehicles in the middle or rear of a queue.