Collision-Free Autonomous Scheduling at Unsignalized Intersection Using Conflict Graph Tree Search

The autonomous scheduling at unsignalized intersections faces a great challenge for ensuring collision-free passing and improving traffic efficiency under the complex intersection environment and heavy traffic density. In this article, we first design an autonomous management model for unsignalized intersections which uses the intersection control center to manage the passage of vehicles instead of traffic light. To avoid vehicles collision, the intersection is divided into multiple collision subzones, and each collision subzone needs to satisfy that the occupancy time of different vehicles is not overlapped. Second, a conflict graph tree search (CGTS) algorithm is developed to attain the optimal passing priority, which has the highest traffic efficiency. The CGTS algorithm reduces the computational complexity by compressing the solution space and reducing repeated calculations. Then, a heuristic threshold-based motion control strategy is proposed, which supports vehicles to reach the intersection at the assigned time by controlling their acceleration. Finally, we perform simulation experiments to show that the effectiveness of our algorithm outperforms comparison algorithms at various traffic densities.