Reasearch On Vehicle Conflict Detection And Resolution Algorithm At Unsignalized Intersection

Traffic safety on the road intersection has been a common challenge in various countries,and the problems of intersections has troubled many scholars. Because the intersectionscomposed by different directions of the road is an important traffic hub in a road net, and manyvehicles steer freely at the hub, which is easy to produce different traffic conflicts. So the traffichub is accident-prone area. Now, the research beased on intersection safety is focused on thetraffic impact factors, such as people, vehicle, road and transportation environment and theirrelationships with traffic accident. In order to improve the traffic safety, researchers use theanalysis results to perfect the road design, improve the traffic control measures, or install theactive/passive safety devices on the vehicles. But the traditional design, control andmanagement technology can only take effect on some problems in a certain extent, such asreducing the number and severity of traffic flow conflict, which couldn't prevent accidents,achieve the optimal safety profits, or even solve the traffic problems in essence effectively,especially have little effect to improve traffic safety at unsignalized intersections.With the technical development of the GPS, wireless communication and intelligentvehicle, VII (Vehicle Infrastructure Integration) has been becoming an effective means to solvethe traffic problem. Under the VII environment, information sharing and interactivity can beachieved via V2V (Vehicle to Vehicle communication) and V2I (Vehicle to Infrastructurecommunication). Multi-vehicles cooperation can accomplish risk detection and evaluation,avoiding the traffic accidents. For example, the vehicles at intersection can communicate withthe traffic lights via information sharing and interactivity can be realized via V2V and V2I, toget acknowledge whether can it passes the green-signalized intersection safely, and to get rid ofdilemma zone; The leading vehicle conveys its starting information to the following vehicle,toinduce the waiting time and increase the intersection capacity. Between the running vehicles tothe same direction, the leading vehicle conveys its braking information to the following vehicle,avoiding the rear-end accidents. In the changing line process, the vehicle determines the propertiming to change line by sensing the status of vehicles around, to increase the driving safety.Nowadays, VII has been the research focusing on global intelligent traffic field, leading thedevelopment of the intelligent traffic, and greatly improving the traffic safety.This dissertation, which is sponsored by the National High Technology Research andDevelopment Program (863) (No. 2011AA110403), focus on the traffic safety peoblem on road intersection. On the basis of VII, two vehicles conflict detection and resolution strategies at anunsignalized intersection are innovatived, which eliminate conflicts before they turn intoaccidents. It provides a theoretical basis for the realization of multi-vehicle cooperative control.The major research work includes the following aspects:(1) Vehiceles conflict identification method based on vehicle to vehicle communicationis researched. At first, vehicle appropriate positioning method and technique of GPS coordinatetransformation are analyzed. Then the problem about the coordinate transformation fromWGS84 coordinate system to the plane coordinate system is discussed.The kinds of informationthat need to get between the vehicles is determined, including vehicle location (latitude andlongitude), speed, acceleration, heading angle, and vehicle size. Kalman filtering method andvehicle kinematic equations are analysed, and a vehicle trajectory prediction equation isestablished based on Kalman filter. After vehicle information collection system is builded, realvehicle experiment is carried out. The experiment results show that accuracy of the proposedvehicle trajectory prediction equation. Then a vehicle collision detection method consideringthe vehicle's dimension is established, and TTC (Time to collision) is selected as an indicator ofthe degree of vehicle conflict risk.(2) Traffic rule of unsignalized intersection is designed. The vehicles conflicts at thecrossing are classified, and then the characteristics of intersection accidents caused by thevehicles conflicts are analyzed. Based on the Road Traffic Safety Law, passage rules of theintersection when the vehicle will go straight, turn left, turn right and so on are researched. Andthen passage rules of the unsignalized intersection are designed.(3) Vehicle conflicts resolution models are designed. Atheoretical analysis about conflictresolution of the two vehicles is carried out. It is pointed out that the vehicle conflict, in essence,is two vehicles which will pass through the intersection at the same time, which means that theyhave the superimposed part of time and space. If one of them appropriately regulates the timeof entering the intersection, it will effectively prevent two-vehicle collision accident. Afteranalyzing disadvantages of the existing intersection collision algorithm, the confluence conflictand cross-conflict resolution model are designed according to the unsignalized intersectionrules to make sure the veihicles at intersection driving safely. These models determine the timeand sequence of passing through the intersection for different vehicles.(4) Simulation experiments of multi-vehicle cooperative conflict resolution atunsignalized intersection are researched. Multi-vehicle coordination problem under vehicle tovehicle wireless communication environment is reseached, and multi-vehicle cooperativeconflict resolution decision-making process at unsignalized intersection is designed. Then amulti-vehicle coordination control simulation system is built by using PreScan software and the vehicles conflict detection and conflict resolution model simulation experiment is carried out.In the simulation experiment, three cases of multi-vehicle cooperative conflict resolution aredesigned. The vehicle which has low priority should adjust its velocity according to the statusof the vehicle which has high priority to pass the intersection. The simulation results show thatall of the vehilcles can pass through the intersection without collision, which means that motionof individual vehicles can be conducted in a safer, more deterministic and smooth mannerunder cooperative conflict resolution guidance. Simulation results indicate that the proposedconflict resolution algorithms have the potential for actual applications in driving at blindcrossing. In addition, the factors (Vehicle dimensions, vehicle positioning errors, informationtransmission delay, etc.) that affect the conflict resolution strategies are analyzed, and thenfurther amendments of the conflict resolution model are researched, which provides a basis forimproving the efficiency and reliability of the conflict resolution strategies.