Optimization Method Of Signal Control Adapting To Stretching-Segment Length

Signalized intersection is one of basic elements of composition of the whole urban road network, traffic efficiency of the whole urban road is mainly determined by the operation of each signalized intersection, how to raise the efficiency of intersection and then improve the traffic of the whole urban road network has become difficulty of traffic management and control. Set up stretching-segmentto increase lane number is the efficient method for improving the capacity of intersection, despite that the design of stretching-segment at home and abroad has already set corresponding standard, because of limitation of urban road space and the randomness and variability of traffic flow, overflow for the vehicles on stretching-segment has become common traffic phenomenon, how to make storage length of stretching-segment and signal timing programcoordinate one the other has become a important problem. This dissertation studies on the design of the most common planar crisscross signalized intersectionstretching-segment and the signal control program and the coordinating relationship of them, especially studies on the inter-constraint rule of them and the optimization of signal timing parameters. In the light of above contents, this dissertation makes studies on the following four aspects.(1) Analysis on effect ofstretching-segment design to traffic flowDesign principle of approach channelization is summarized, and from it the thread and method for stretching-segment design at home and abroad are gathered, the characteristic and the advantage and disadvantage of different methods are analyzed contrastively, the problems existing in actual application of stretching-segment design are found, which is the background of further study on effect of stretching-segment design to traffic flow.Many intersections with different stretching-segment design forms are selected to study on saturation flow rate at peak rush hour and ordinary time hour, the characteristic of saturation flow rate in green time is analyzed under two conditions, overflow and underflow of vehicles on stretching-segment. According to the research result, the change laws of saturation flow rate are significantly different with different stretching-segment design forms under otherwise equal conditions, and make this practical observation law as theoretical basis for study on effect of stretching-segment design to traffic flow.In the view of underflow of vehicles on stretching-segment traffic condition, the particularity of flow rates in green time is analyzed in brief. In the view of overflow of vehicles on stretching-segment traffic condition and combine practical observation law, following models are found by using traffic flow theory and stochastic mathematics principle:probability model ofstraight flow hindered byleft flow and mathematical expectation model of hindered straight vehicle; probability model of left flow on exclusive left-turn lane hindered by straight vehicle and mathematical expectation model of hindered left-turn vehicle; probability of right-turn vehicle on straight and right-turnsharedlanehindered by straight vehicle and mathematical expectation model of hindered right-turn vehicle. At last attenuation laws of saturation flow rate in green time are obtained from hindered laws of traffic flow, and make this as reference basis for setting ofsignal timing parameters.(2) Setting of signal timing parameterswith consideration of stretching-segmentdesignDesign basis of phase sequence with consideration of stretching-segment design forms and algorithm of cycle green ratio are studied, in addition, setting of interval green time is studied in detail. The main contents are as follows:Design principle and method of common crisscross signalized intersection phase sequence is summarized, find out there is a lack of consideration of store length factor on stretching-segment in designing of straight left phase sequence, as a result, preliminary analysis of hindering condition of traffic flow based on conditions such as flow and flow direction before designingsignal timing program is put forward, and make this as one of the basis of setting of straight left phase sequence.Definition and setting method of interval green time at home and abroad is described, in the view of it drawbacks and considering predicament area, enter time and empty time, setting thread of minimum interval green time is put forward and mathematical model is set up, effect of enter speed, speed limit, type, intersection geometrical space, traffic condition to interval green time is quantitatively analyzed, the range of necessary setting and unnecessary setting of interval green time at intersection is obtained, at last take one intersection in Changchun city as a example to show the efficiency of mathematical model of interval green time.After confirming the design principle of phase sequence and calculation method of interval green time, existing calculation method of cycle and green ratio is improved, effect of length design of stretching-segment to saturation flow rate is taken into special consideration.(3) Evaluation of operational effect at intersection with consideration of stretching-segment designThe advantages and disadvantages of classic delay formula at home and abroad and its applicability range are analyzed, improvement of delay formula with consideration of vehicle arrival sequence is made. In the view of underflow of vehicles on stretching-segment traffic condition, delay mathematical model of right-turn vehicle on straight and right-turnsharedlane and total delay model of straight and right-turnsharedlane are set. In the view of overflow of vehicles on stretching-segment traffic condition, delay mathematical model of left-turn vehicle with consideration of hindered vehicle and delay mathematical model of straight vehicle with consideration of hindered vehicle driving on neighboring lane, relative to existing method, both vehicle arrival sequence and the fact of increasing in the number of lanes on stretching-segment are taken into consideration. At last efficiency of delay mathematical model is verified by simulation method.Existing computational method of capacity is modified based on previous effect of store length of stretching-segment to saturation flow rate. Double-objective optimization model of signal timing parameters using delay and capacity as target function is set up based on previous mathematical model of delay and capacity with consideration of store length of stretching-segment, and optimization scheme is verified by simulation method.(4) Optimum method of signal timing parameters under special conditionsWhen it is unable to coordinate intersection space supply and time supply only by optimization of cycle and green ratio, the solution of phase sequence optimization and changing channelization design are put forward. In the case of unconditional changing channelization design, put forward eliminating the interference among upper traffic flow on stretching-segment by one-port release or releasing many times in a cycle, and roughly obtain the applied characteristic and result of this method by simulation method. In the case of conditional changing channelization design, put forward the solution that cancel increasing in number of sequential lanes on stretching-segment and to eliminate the interference among upper traffic flow on stretching-segment.In the last, the main progress and achievement of this dissertation are summarized, and the contents and problems which need to perfect and explore further more in the study are put forward.