Towards Implementation of Max-Pressure Signal Timing on Minnesotan Roads

Project summary:

Hennepin County, along with other cities and counties in Minnesota, has been updating their signal controllers with adaptive timing capabilities that can respond to real-time detection of vehicle queues. The open question is how to set signal timings to improve throughput, delay, and other measures of effectiveness. This project will leverage recent theoretical work on max-pressure signal control, which defines a phase selection that is provably throughput-optimal for networks, to maximize the number of vehicles moving through a corridor or a network.

Although the proof is highly complex, the timing itself is simple. A pressure value is calculated for each phase based on queue lengths, and the phase with the greatest pressure is selected for the next time step (e.g. 10-30s). Max-pressure control is adaptive because the next phase is determined in real time. Max-pressure control is also computationally efficient because it is decentralized, i.e. the timing at each intersection only depends on the queue lengths on links immediately upstream and downstream.

Despite the potential benefits, max-pressure control has appeared only recently in the literature and is currently primarily theoretical. It has not been used in practice and there are a number of practical issues surrounding its implementation, ranging from assumptions in the analytical formulation to evaluating its effectiveness on roads. These include unbounded waiting times, lack of pedestrian access, lack of simulation in city networks, and implementation challenges in signal hardware. The purpose of this project is to investigate and resolve pressing issues and move towards a pilot study on intersections or corridors in Minnesota.