Research On Adaptive Control Model And Algorithm Of Roundabout

As an important intersection form, roundabout has played an important role in theprocess of urban development. However, with the increasing of urban traffic, thenon-signalized roundabout is easily blocked. In addition, the traffic jams, disorder,accidents occured frequently during the peak hours. To solve this problem, trafficengineers are usually install signal lights at the intersection, there are the singlet signalcontrol and turn left at the second stop line control. Which the former is generally atwo-phase or four-phase with mutual influence of the vehicles. The latter is a newtraffic-signal control method, but it has high requirements of intersection geometry andtraffic condition, when the left turn ratio is high, it easily cause the intersection todeadlock.In order to explore new control method of roundabout, this paper first reviews therelated study of roundabout and signal control theories, and analysis the shortcomingsof existing studies.Then investigate the operation status of roundabout in Chongqing. On the basis offully understanding of the roundabout’s geometric properties, the author divided theroundabout into four categories according to the center of its island, and analyses theimport area, export area, circulation area and weaving area of signalized andnon-signalized roundabout of all sizes. Put forward a single-import clearance adaptivecontrol model based on rules and optimization model, this control method has no fixedphase, it selects the next green phase and assigns green time to it according to the trafficflow information at the end of each phase. Based on single-import clearance adaptivecontrol model, the author then designed a multiple-import clearance adaptive controlmethod with phase combination scheme more flexible.Finally applicate VISSIM4.3to simulate, the results show that under differentflow equilibrium degree, the single-import clearance adaptive control model hasobvious advantages over the other two control method on reduce delay and queue length.And under unsaturated traffic condition, multiple-import clearance adaptive controlmodel has obvious advantages on reduce average delay and queue length compared withthe singlet signal control, it has obvious advantages on reduce average delay but onlyslight advantage on queue length compared with the turn left at the second stop line control. The main reason is that turn left at the second stop line control can let some leftturn vehicles queuing in the circulatory roadway. Examples of intersection simulationalso verifies the effectiveness and feasibility of the research.