No abstract

This study proposes a new adaptive traffic signal control scheme to effectively manage dynamically fluctuating traffic flows through intersections. A spatial-temporal representation of the traffic state at an intersection has been designed to efficiently identify traffic patterns from complex intersection environments, and a deep neural network (long short-term memory network, LSTM) is used to determine look-ahead signal control decisions based on the estimated long-term feedback from a given traffic state. The actor-critic algorithm, one of the reinforcement learning-based algorithms, is adopted to obtain the essential parameters of the LSTM deep neural network through multiple interactions between a simulated environment and the corresponding adaptive traffic signal controller. A realistic model environment comprising a 24-hour time-varying traffic demand including rush hour and non-rush hour situations served as the basis for traffic generation in the numerical experiments to confirm the effectiveness of the proposed scheme. The results of these experiments show that, compared to an optimized fixed time plan (Synchro), the proposed scheme can reduce waiting times at intersections by an astounding 50% with consequential benefits of reducing fuel consumptions, emissions, queue lengths, and vehicle delays whilst increasing mean speeds.

Lane-changing is a basic driving behaviour, which largely impacts on traffic safety and efficiency. With the development of technology, the automated lane-changing system has attracted extensive attention. Among it, the trajectory planning part is a challenging problem owing to the complexity and diversity of the driving situations. The planner requires the real-time capability to produce safe and comfortable trajectories for coping with the dynamically changing environment. Based on this, the paper proposes a lane-changing trajectory planning model in dynamic driving environments. The model constructs a neural network to predict the end position of the ego vehicle, and then adopts the mathematical programming method to solve the optimal lane-changing trajectory that guarantees the ride safety and comfort. With the assistance of the neural network, the lane-changing trajectory planning problem is converted into a quadratic programming (QP) model, thereby achieving rapid solution of the model. Moreover, to train the proposed algorithm, a novel approach for generating the scenario data is designed, which can generate rich and diverse traffic scenarios at a low cost. The simulation results show that the proposed model can plan a lane-changing trajectory quickly and effectively, and the ego vehicle can follow the planned trajectory safely and comfortably.

Recently, automated vehicles have been recognized as a promising tool to address the problem of on‐ramp merging. However, the complexity of the problem includes ignorance of the vehicle's lateral dynamics, the limitation of the fixed merging point, the mismatch problem caused by the sequential optimization scheme, and the fixed terminal states assumption. These factors make it intractable in practical driving scenarios. This paper proposed an integrated optimization model for on‐ramp automated vehicles, which can guide the vehicle to complete the merging behaviour from the ramp lane to the main lane safely and efficiently. A merging path is first constructed in the two‐dimensional plane with two critical parameters recommended by a neural network predictor, enabling it to incorporate both longitudinal and lateral dynamics. Then, an integrated Mixed Integer Quadratic Program (MIQP) model is built to determine the optimal velocity profiles and merging gap simultaneously while considering the safety and efficiency factors. Specifically, with the introduction of discretization and linearization techniques, linear collision avoidance constraints and smooth transition constraints can be built, which can address the challenging computational problem. The effectiveness of the proposed model is validated through the microscopic and macroscopic numerical results under different levels of mixed traffic.