Hierarchical Centralized/Decentralized Event-Triggered Control of Multiclass Traffic Networks

Two hierarchical control schemes for regulating traffic in freeway networks via ramp metering are developed in this article. Both schemes are characterized by a multiclass nature and aim to jointly improve the total time spent by the vehicles and their pollutant emissions in the freeway network. Moreover, these schemes have been designed to be “implementation-oriented,” i.e., they are characterized by a low computation and communication effort of the controllers while providing high performance in case of bottlenecks that may be far downstream on-ramp merging areas. The reduction of the computation and communication load is achieved through an event-triggered logic implemented at the higher level of the hierarchical scheme, in which the lower level is represented by extended multiclass ALINEA controllers characterized by time-varying parameters. The two proposed schemes differ for the fact that one is a centralized scheme, whereas the second one is decentralized. The effectiveness of the two schemes is evaluated by simulation in a realistic setting, also through a comparison with an optimization-based approach.

I. Introduction

The efficient management of freeway traffic networks has become a very relevant issue all over the world in order to tackle the continuous growth of traffic congestion and the resulting negative consequences for human life in terms of pollutant emissions, fuel consumption, accidents, and noise. For these reasons, advanced technologies and methodologies have been designed by researchers and are still under development to provide travelers with a safe, sustainable, coordinated, and smart mobility system. These solutions are mainly related to the design of new infrastructures, the advancement of new technologies in the automotive sector to produce safer and less impacting vehicles, as well as the development of traffic control measures that enable the efficient use of the present transport infrastructure by exploiting the modern information technology systems [1].