The Ramp Control Model Based On Beltway Traffic Flow Characteristics

China's beltway has the following problems:(1)The composition of beltway internal traffic flow change from the original vast majority of urban transit vehicles into most of the vehicle access to the city;(2)The vehicles from the original vast majority of medium-sized truck turned into dominated by the car traffic composition;(3)The rush hour,holidays trip traffic jam frequent happen on the beltway;In regard to this traffic problems urgent need to solve,No effective achievements to control beltway traffic flow or ring road traffic flow at home and abroad.Internal beltway can be regarded as a closed system,It is only related to the traffic flow of entrance ramp and whether the on-ramp control.Therefore: Paper's key contents are as follows:Paper classified studied the basic theory of single ramp control,single ramp control is the use of traffic flow conservation physical model relations,traffic speeds,density relation,dynamic traffic transfer equation et al describe the traffic flow state,by controlling the ramp control rate,so that the main line of traffic,the total delay time of a ramp TTS minimum control model.Analysis of the traffic composition beltway traffic flow,relationship between speed,flow,density,considered the establishment of the multi-interval single ramp control META improved model,that the traffic density short period after a ramp into the main line of traffic will increase as traffic subsequent runs to give self-regulation,the entrance ramp control rate shall be determined by the self regulating ability of the multiple operating range between the current ramp to the next entrance ramp.Paper compared Total Time Spent(TTS)and the Total Waiting Time(TWT)of the Qujiang interchange section from Xi'an beltway with control or not without ramp control,found the multi-interval single ramp control META improved model has better control results in a non-congested state,and low traffic density state,and analyze the reasons for poor control effect is any single common ramp control.This commonality is: When the mainline traffic density is low,single ramp control effect tends to no state control;when the mainline traffic density is large,ramp control law is small,the TTS basic depends on the state of mainline traffic,the TWT can be controlled very limited space.And any single ramp control is a passive control,It can not determine a new ramp traffic delays is whether formed by upstream ramp traffic density and downstream ramp or not.Paper considered the structural characteristics constitute a closed system of beltway,proposed a model applicable to ramp control ring road network with entrance limited,as the principle that driver in the one-way loop will not select exports from entrance no more than 1/2 of the total length of the loop,get all the OD matrix demand of entrance ramp on mainline,in conjunction with the entrance ramp traffic flow and the traffic flow between each mainline,get all the proportion of exit traffic flows from on-ramp to off-ramp,so that both arbitrary interval mainline traffic flow and off-ramp traffic flow can be expressed by on-ramp traffic flow.When the main line of traffic congestion occurs or insufficient capacity at off-ramp,it all can launch anti-traffic source,by combining the ramp control model,target to the TTS minimum,efficient operation of ring expressway mainline traffic and reduce queuing time of on-ramp.As the results of Xi'an unidirectional beltway central Link,showed control model in this paper is effective.