| As the jump in travel demand in recent years,the contradiction between traffic demand and traffic infrastructure is increasingly prominent,massive congesti on on the super highway before and after the holiday have become common.Entering ramp is the main entrance of freeway,and the running state of the traffic flow at the upstream and downstream of the ramp will influence the operation of the main road.The detailed research on the traffic flow at the ramp can be the base of the control strategy of the entering ramp.And a reliably entering ramp control strategy can relieve the congestion caused by vehicles which merge onto the main road from the on-ramp and guarantee the running efficiency of the main road.Thus a reliably on-ramp control strategy which based on the research of micro-features of traffic flow can make a great different on the super highway construction and management.This paper simulated the super highway and the entering ramp in the theoretical frameworks of Three-phase Traffic Theory,and proposed a on-ramp control strategy.The main points of this paper are summarized as following:(1)This paper compared the cause o f congestion at bottleneck of super highway in traditional traffic flow theory and Three-phase traffic flow theory,and made a summing up of the explanation for different theory.(2)This paper presents a newly-modified KKW model,including the subdivided vehicles types,and introduces the changes for a driver’s sensitivity into the speed fluctuation.By means of the numerical simulation,the following conclusions are obtained herewith: the speed disturbance can disturb the driving behavior of following vehicles,but the disturbance will dissipate quickly in free flow phase.However,the disturbance can propagate upstream and spread to the whole main road in synchronized flow phase.Besides that,this paper found that the aggressive drivers’ driving behavior can intensify the disturbance,and the conservative drivers’ behavior can weaken the disturbance in free flow phase.But in synchronized flow phase,the preferences of drivers’ behavior can make little influence on the propagating of the speed disturbance.(3)Introducing the lane-changing rules,the model was extended to a two-lane CA model.During the simulation,this paper found that lane-changing rules can make the road source used more efficient.For this reason,the critical flux in two-lane model is higher than the value in the one-lane model,and the flux curve of two-lane model is smoother.Besides that,this paper found that the lane-changing behavior can make different influence in different phases.If the traffic density is lower,the lane-changing behavior will not influence the operation of traffic.As the increasing of the traffic density,the lane-changing behavior can cause and dispel the congestion gradually,which is so-called dual function of lane-changing.(4)This paper analyzed the influence caused by the vehicles merged from the on-ramp under an open-boundary condition.This paper found that as the increasing of the flux of on-ramp,the average speed of the whole main road will drop.And after the average speed and flux of the main road keep stable,the flux of the on-ramp is no longer impact the main road obviously.This paper also found that the vehicles marge onto the main road from the on-ramp can cause the speed disturbance and peed speak too.And the speed disturbance and speed peak both spread upstream,but the functions of the two are poles apart.Speed disturbance can lead to a localized F ?S transition,and the speed peak can cause a localized S ?F transition.Based on this,this paper thought the velocity distribution features are different on different characteristic obvious points,and proposed an on-ramp control strategy. |
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