A single-layer approach for joint optimization of traffic signals and cooperative vehicle trajectories at isolated intersections

Meiqi Liu,Jing Zhao,Serge Hoogendoorn,Meng Wang

doi:10.1016/j.trc.2021.103459

Abstract

A joint control approach that simultaneously optimizes traffic signals and trajectories of cooperative (automated) vehicle platooning at urban intersections is presented in this paper. In the proposed approach, the signal phase lengths and the accelerations of the controlled platoons are optimized to maximize comfort and minimize travel delay within the signal cycle, subject to motion constraints on speeds, accelerations and safe following gaps. The red phases are initially considered as logic constraints, and then recast as several linear constraints to enable efficient solutions. The proposed approach is solved by mixed integer linear programming (MILP) techniques after linearization of the objective function. The generated outputs of the MILP problem are the optimal signal timings and the optimal accelerations of all vehicles. This joint control approach is flexible in incorporating multiple platoons and traffic movements under different traffic demand levels and it does not require prespecified terminal conditions on position and speed at the signal cycle tail. The performance of the proposed control approach is verified by simulation at a standard four-arm intersection under the balanced and unbalanced vehicle arrival rates from different arms, taking the released traffic movement numbers, turning proportions, signal cycle lengths and the controlled vehicle numbers into account. The simulation results demonstrate the platoon performance of the joint controller (such as split, merge, acceleration and deceleration maneuvers) under the optimal signals. Based on the simulation results, the optimal patterns of trajectories and signals are explored, which provide insights into the optimal traffic control actions at intersections in a cooperative vehicle environment. Furthermore, the computational performance of the proposed control approach is analyzed, and the benefits of the proposed approach on the average travel delay, throughput, fuel consumption, and emission are proved by comparing with the two-layer approaches using the car following model, the signal optimization models, and the state-of-the-art approach.

Highlights

Introduction and motivationTraffic lights are one of the fundamental elements on urban roads for traffic management
Multiple simulation experiments are designed to validate the performance of the control algorithm, taking into account the overall controlled vehicle numbers N, the maximal numbers of the released traffic movements Tmmax, and the signal cycle lengths C
It is observed from simulation results that the control objectives are fulfilled and all constraints are satisfied under different traffic demand levels with the balanced or unbalanced arrival rates from different legs, and the proposed controller has the flexibility in incorporating various cycle lengths, signal phase sequences, and turning proportions

Summary

Introduction

Introduction and motivationTraffic lights are one of the fundamental elements on urban roads for traffic management. The red phases are beneficial to separate conflicting traffic movements at intersections, but they cause substantial travel delay, fuel consumption and emissions on urban roads (Zhao et al, 2020). To relieve these problems, the recent advances in connected and automated vehicle (CAV) technology have attracted considerable attention. ✩ This article belongs to the Virtual Special Issue on IG005581: VSI:MFTS. Numerous studies have investigated the cooperative design of traffic signals and/or CAV trajectories at signalized intersections taking advantage of CAV technology

Results

Discussion

Conclusion