Supervisory multi-class event-triggered control for congestion and emissions reduction in freeways

The paper addresses the problem of regulating traffic in freeway networks via multi-class ramp metering with the objective of reducing both congestion and traffic emissions. The proposed control scheme includes a supervisor, acting at a higher level, which receives measurements from the network and periodically makes a prediction on the system evolution. At the lower level, local feedback controllers compute the control action on the basis of measurements in a neighbourhood of the on-ramp. The neighbourhood is communicated by the supervisor in real time, according to an event-triggered logic. The effectiveness of the proposed control scheme is assessed through simulation results, properly discussed in the paper.

I. Introduction

The increasing number of vehicles in freeways has caused, in the last decades, not only an intensification of congestion phenomena but also a strong growth of pollution, with immediate negative impacts on citizens' health and quality of life. Therefore, the development and implementation of management and control tools is nowadays particularly urgent to make the traffic systems more sustainable. A very effective and widespread control measure for freeways is ramp metering, which allows to regulate the traffic volume entering the mainstream from on-ramps through the use of traffic lights. Researchers have studied different ramp metering controllers for freeway traffic systems, in order to minimize travelling times for the drivers [1]–[4], and, more recently, also to reduce pollutant emissions or to increase safety [5]–[7].