Models And Simulations Of On-ramp System Under Signal Controlling

Bottlenecks play an important role in affecting the traffic, because most of the traffic jams are concerned with the bottlenecks. Experimental observations suggest that close to the bottlenecks there were many complicated traffic phenomena frequently. When the vehicles arrive at a bottleneck, the free and stable traffic will be disturbed, and evolves into different congested traffic patterns. To the variety and complexity of the traffic patterns induced by the bottlenecks, many of the questions are still not well understood. To know what the mechanisms behind the complex traffic phenomena, further investigations and discussions are needed. Especially, ramp is one of the classical bottlenecks. In this paper, by using the cellular automata method we have established the models and simulations of on-ramp system under signal controlling and made detailed numerical experiments with the models. We analyzed the traffic behaviors near the bottlenecks and put forward some suggestions for the signal controlling method in on-ramp system. The contents of the paper are follows:1. The traffic signal is setup at the merging part between the main road and the on-ramp so that it can control the vehicles of both the roads, it can enhanced the capacity of the on ramp system effectively. The past research discussed the single-lane situation only, while the major deficiency of single-lane models is that overpass is forbidden. In this paper, we extended the on-ramp system of single-lane main road under signal controlling to the on-ramp system of two-lane main road under signal controlling by introducing the rational lane changing rules. We study the traffic behavior of on-ramp system with two-lane main road under signal controlling. We simulate the effect of traffic signal on vehicle flows of main road and on-ramp, traffic capacity and average velocity at the merging part are discussed. Through the analysis of the phase diagram, it can be find that the on-ramp system with two-lane main road can embody more complicated and realistic traffic flow characteristics than the on-ramp system with single-lane main road. Compared with the model by Jiang [Jiang R 2003 J. Phys. A 36 11713], the simulation results indicate the state of traffic flow has been improved obviously and the capacity of the on ramp system has increased.2. To the on-ramp system under signal controlling, the past research only considered the method of controlling passage time of green signal of vehicles on the main road and on-ramp by probability that vehicle enters from the left boundary of main road and on-ramp. Nevertheless, there were many complicated traffic pattern frequently near the ramp, as a result the signal controlling has variety installing methods. Based on this, in this paper, we adopt the method that the passage time of green signal of vehicles is determined by the queuing length of vehicles to control the vehicles of the both roads. We simulate the effect of traffic signal based on the vehicles queuing length on vehicle flows of main road and on-ramp, traffic capacity. The result expresses that compared with the on-ramp system with signal controlling based on probability of vehicles entering, the phase diagram of the on-ramp system based on the queuing length is categorized four regions, and there are some new traffic patterns in the new region. When the main road and ramp are both congested, the current of both roads remain constant respectively without the increasing of the probability of vehicle entering. The simulation results indicate the system under signal controlling based on the queuing length maintain more stability in the traffic evolving processing.