Feed-Forward ALINEA: A Ramp Metering Control Algorithm for Nearby and Distant Bottlenecks

This paper proposes a new ramp metering control algorithm, Feed-Foward ALINEA (FF-ALINEA), for bottlenecks located both nearby on an on-ramp and further away from it (i.e., more than just a few hundred meters). The formulation of the controller is based on a feed-forward modification of the well-known control algorithm for ramp metering, ALINEA. The feed-forward structure allows anticipating the future evolution of the bottleneck density in order to avoid or reduce traffic breakdowns. The proposed controller is tested, using the macroscopic traffic flow model METANET, for nine scenarios, and the results are compared with the ones obtained with ALINEA, PI-ALINEA, and with the optimal solution. The simulations show that the FF-ALINEA is able to approach the optimal behavior, thereby outperforming ALINEA and PI-ALINEA. Moreover, results indicate that the FF-ALINEA is quite robust in cases where different demands are considered, there are a limited number of available detectors, or there are errors in the estimation of the capacity and/or the critical density of the bottleneck.

I. Introduction

Traffic jams on freeways cause many social and economic problems in daily life, such a waste of fuel and time, an increase in pollution, and greater accident risk. Much research has been focused on solving these problems without constructing new infrastructure, because that choice is not always a viable option or it cannot be afforded. Ramp metering is the most successfully implemented and widely used freeway control measure among the most promising dynamic traffic control measures (such as variable speed limits [1], reversible lanes [2], route guidance [3],). Ramp metering has already been successfully implemented in practice in France, United States, Germany, Australia, and several countries [4], [5].