Research On The Method Of Coordinate Control For Oversaturated Arterials

Nowadays, the China’s vehicle population and the total urban road traffic increase sharply,in peak hours the center city’s main roads are mostly saturated, and the vehicle speed is only10-15km/h. Traffic congestion caused vehicle travel delay increased, speed reduced, while thevehicle is consuming more fuel and discharging more pollutant emissions in a low speedenvironment than the normal drive. The congestion evokes traffic accidents more easily, whilethe accidents aggravate congestions to a vicious circle. The exacerbated traffic congestionleads to the city’s huge economic losses and restrictes the further development of the urbaneconomy. Therefore, the study of oversaturated urban traffic conditions has become a toppriority of the study.The paper startes from the difinion of the oversaturated traffic state, compares the controlobjectives and optimize parameters in the non-saturated state with those in the oversaturatedstate, discusses three characteristics in the oversaturated state, which are dynamic, queuingspread and defacto red, divides the research into the single diretion oversaturated control intidal flow and the normal oversaturated arterial problem, analyses the timing control andreal-time control in the oversaturated coordination and finaly shows that the real-time controlis more conducive to the ovesaturated coordination.For the oversaturated control in tidal flow, based on the flow-sharing and trafficmanagement strategy, a mixed-integer linear programming model is established by using themethod of time-space analysis, which can carry out green wave control and red wave controlfor different directions in arterial road. The various traffic control needs can be satisfied toadapt to different traffic conditions by adjusting the red wave weighting factor in the objectivefunction. The optimal solution of the model can be achieved by use of LINGO software andprogramming language. The example effectively demonstrates that the model can maximizethe bandwidths of green wave and red wave for different directions.For the normal oversaturated arterial problem, the ideal offset is determined by the drivingcharacteristics of the queuing and reach traffic flow, the green time is determined to meet thetraffic demand and avoid the intersection block, the queuing vehicle factors are determined bythe different control strategies, the main direction coordination control model in arterial is builtby the goal of the release of imports and exports. Based on the model, there is three states inthe intersection’s secondary direction, which are blockage, new traffic and wasted green, thesekinds can determine eight different combinations, and their offset, green time and output iscomputed in the secondary direction. The bidirectional coordinate control model for oversaturated arterial is built by the combination of the control conditions of two directions.The optimization solution process of the bidirectional coordinate control model is showedby the illustrative example, the problems existed in the global solution is analyzed, and the fastsolving method is proposed by the use of genetic algorithms and descending. Using VBlanguage program the example’s timing solution is get by the descending method, and theoutput and queuing vehicle is analzed for each strategies. Finally, verify the validity andaccuracy of the model by the comparion of the ouput, queuing vehicle and greenwave effectsunder the four strategies.