Study On Coordination Control Method For Preventing And Evacuating Spillover Of Oversaturated Traffic Networks

As the city scale expanding and the rapid growth of traffic demand the traffic networks often is oversaturated. Spillover often happens in oversaturated traffic networks. It can lead to the emergence of congestion in traffic networks and even paralysis. So based on the analysis of the traffic characteristics in oversaturated traffic networks the control strategies and the optimization algorithms for preventing and evacuating spillover are needed to be researched. It has important theoretical significance and practical value to improve the running efficiency of traffic network. In this paper the traffic flow characteristics about oversaturated traffic networks are provided. The 7 section macro simulation model describing spillover is funded as the simulation platform. The coordination control theories preventing and evacuating spillover about oversaturated traffic artery and preventing and evacuating spillover coordination control theory about oversaturated traffic networks are researched. The main work and innovations are summarized as follows:1. The definition and the computing method of oversaturation index are presented.The traffic flow operation between the adjacent intersections is analyzed by traffic wave theory. Phase oversaturation index and intersection oversaturation index are defined and the calculation methods of those are given.Two adjacent intersections in Pearl River new town of Guangzhou are simulated. The results show that the indexs are reasonable and can reflect the degree of oversaturation of the intersection or phase.2. The 7 section macro simulation model describing spillover is funded. This model includes seven operation stages. The seven operation stages respectively are external demand, upstream demand, driving lane, join groups, through intersection, leave output section and flow conservation. The five parameter logarithm density-speed model is provided and used in driving lane stage. It is a single function which can accurately describe the speed changes from the maximum density to the minimum density. The calculation method of the traffic flow enter intersection considering the capacity of intersection and the traffic flow departing intersection considering spillover are presented in through intersection.The model is simulated.The results show that the model can reflect the running status of traffic flow and can describe the spillover.3. The coordination control theory preventing and evacuating spillover about oversaturated traffic artery is presented. Aiming at preventing spillover about oversaturated traffic artery the coordinated control method of the oversaturated traffic artery based on the preventing spillover offset is studied. The design of preventing spillover based on the ideal offset and the coordinated control model based on preventing spillover offset are given. Step by step optimization algorithm is put forward according to the characteristics of the model. In this algorithm the differential evolution initial bacteria foraging optimization algorithm is used to determine the cycle length. The weighting method is used to predict traffic flow and to calculate the splits of each intersection. The offset constraint processing is executed to get the preventing spillover offset. The model and algorithm are simulated are simulated in the artery consisting of four road intersections in Huasui road in tianhe district, Guangzhou.The results show that the method can keep the offset in the ideal state dynamically and prevent the spillover. It ensures the greater capacity and the smaller vehicle delay compared with other method.Aiming at evacuating spillover about oversaturated traffic artery the control method to evacuating spillover of the oversaturated traffic artery based on POSI is presented. When the spillover along one direction happens the traffic flow is limited in the upstream and is discharged in the downstream. The red time and green time of upstream and downstream are adjusted according to the POSI. The evacuating spillover control model is funded with the objective of the maximum capacity and the constraint condition of available time of conflict phases. The forward and reverse two-stage method is designed to solve the model.The control method to evacuating spillover is simulated in the artery consisting of four road intersections under the larger initial queue and the traffic demand for mutations.The results show that output vehicles has increased and delay has decreased after the evacuating spillover control.4. The coordination control theory preventing and evacuating spillover about oversaturated traffic networks is presented. Aiming at preventing spillover about oversaturated traffic networks the preventing spillover multi-objective oversaturated traffic networks control method based on the HPSO algorithm is presented. This model has three objectives wich are no spillover, balance delay and maximum capacity. The HPSO algorithm is designed to solve the model in which the offset is optimized by PSO and green time is optimized by simulated annealing algorithm.The model and algorithm are simulated in the road network of nine intersections. The results show that the method can prevent spliiover in the regional road and achieve delay balance and the largest capacity.Aiming at evacuating spillover about oversaturated traffic networks the control method to evacuating multidirectional spillover in the oversaturated traffic networks is presented. When the spillover along cross directions happen the evacuating spillover control model along critical path is funded. The maximum green time of cross directions are used as the objective. The multi-stage method using the cross intersection as fixed reference point is designed. When the spillover along multiple directions happen the evacuating spillover control model along multiple critical paths is funded. The forward and reverse two-stage method using the spillover intersection as centre is designed. The method is simulated in the road network of nine intersections. The results show that this method can evacuate the spillover of the road networks.It also can improve the traffic capacity and reduce delays.