Research On Offset Optimization Of Regional Coordination Control Of Traffic Signal

Regional coordination control of traffic signal is an effective method to alleviate traffic pressure and improve the efficiency of signal control, of which offset is one of the key factors. Therefore, investigating offset optimization of regional coordination control is of great significance. Furthermore, combined with the actual situation of road network in our country, arterial coordination control accounts for an important position in regional signal control. Consequently, this paper investigated offset optimization of arterials, and then promoted it to regional offset optimization, which realize the offset optimization of regional coordination control in traffic signal. The specific research content is shown as below:Firstly, research on arterial offset optimization. The control objective of traditional arterial offset optimization usually takes green-wave bandwidth, or delay as a control objective. It does not build a analytic relation between delay and green-wave bandwidth. Consequently, based on the analysis of vehicle arriving rate and discharging rate, a model of sub-green-wave bandwidth was proposed which takes offset as an independent variable; after that, a linear relation between vehicle delay and bandwidth computed according to this model was built; furthermore, considering the different situation on different road sections, making number of vehicle passing intersections over bandwidth maximum was regarded as a control objective and geometry function was used to distribute forward and backward green-wave bandwidth, which control the bandwidth and delay at same time; At last, it was solved based on the Dynamic Programming.Secondly, research on regional offset optimization. In view of the traditional regional offset optimization did not consider the relationship between vehicles arriving rate and offset, in this paper, an investigation about the condition of the vehicle arriving rate changes over offset was proposed on the basis of network traffic flow model based on cell transmission model; Then, according to the investigation, this paper improve the green-wave bandwidth computation in arterial offset model proposed in this paper, combined with network decomposition method, an offset optimization model which can be adapted to the iterative offset optimization in regional signal control was proposed; at last, the effectiveness and feasibility of this method was analyzed through VISSIM simulation software.Thirdly, comprehensive simulation analysis. For validate the control effectiveness of offset optimization model of region based on arterial overlap, VISSIM simulation software was used to simulate different traffic demands, and compare the optimization effectiveness of the method proposed in this paper with the graphical method and road network without offset optimization. After that, analyze the evaluation indexes in different traffic demands, validate the method proposed in this paper improve the average delay and average stops of the road network a lot comparing with the road network without offset optimization; furthermore, when the traffic demand is relatively high, this method can acquire a better control effectiveness.