Application of Pavement Marker to Avoid Queue-jumping and Traffic Spillback at Off-ramp of Expressways

Urban expressways are connected tightly to local surface/arterial roads through off-ramps and due to the increased traffic volume during peak hour, traffic flows near off-ramps are usually chaotic and difficult to manage. Therefore better understanding of traffic flow behavior at off-ramps is critical to improve traffic management of urban expressways. Drivers’ queue-jump behavior near the off-ramp occurs frequently in developing countries, which contributes significantly to the traffic flow complexity. However, queue-jump behavior is often ignored in the existing microscopic traffic simulation packages. In this paper, the authors develop cellular automata based simulation model, which specifically targets on the traffic spillback and queue jump behaviors near expressway off-ramp. Queue-jump rules are incorporated into the car-following and lane changing logics of the cellular automata model. Using the developed model, the authors simulate different configurations of pavement markings around off-ramp in combination with different off-ramp signal timings. The results show that, although solid pavement markers is designed to reduce the number of discretionary lane-changes, when off-ramp signal cycle is short, the total off-ramp delay is increased, comparing with that of dashed pavement marker. The authors also show that, breaking first in first out (FIFO) queuing (i.e. queue-jump is allowed) will improve the freeway efficiency, which confirms Daganzo’s argument on the damaging effect of FIFO queuing (Daganzo, et al. 2002).