Blue Phase: Optimal Network Traffic Control for Legacy and Autonomous Vehicles

TL;DR

This paper introduces a hybrid traffic control policy for urban networks with both legacy and autonomous vehicles, demonstrating improved throughput and insights into autonomous vehicle market penetration effects.

Contribution

It proposes a novel decentralized hybrid control policy combining green and blue phases, addressing the transitional stage of mixed vehicle traffic.

Findings

The policy maximizes network throughput under demand conditions.

Trade-offs in vehicle travel times depend on autonomous vehicle market share.

Hybrid control improves congestion management over traditional signals.

Abstract

With the forecasted emergence of autonomous vehicles in urban traffic networks, new control policies are needed to leverage their potential for reducing congestion. While several efforts have studied the fully autonomous traffic control problem, there is a lack of models addressing the more imminent transitional stage wherein legacy and autonomous vehicles share the urban infrastructure. We address this gap by introducing a new policy for stochastic network traffic control involving both classes of vehicles. We conjecture that network links will have dedicated lanes for autonomous vehicles which provide access to traffic intersections and combine traditional green signal phases with autonomous vehicle-restricted signal phases named blue phases. We propose a new pressure-based, decentralized, hybrid network control policy that activates selected movements at intersections based on the solution of mixed-integer linear programs. We prove that the proposed policy is stable, i.e. maximizes network throughput, under conventional travel demand conditions. We conduct numerical experiments to test the proposed policy under varying proportions of autonomous vehicles. Our experiments reveal that considerable trade-offs exist in terms of vehicle-class travel time based on the level of market penetration of autonomous vehicles. Further, we find that the proposed hybrid network control policy improves on traditional green phase traffic signal control for high levels of congestion, thus helping in quantifying the potential benefits of autonomous vehicles in urban networks.