Departure rates optimization and perimeter control

Abstract

With the renewed interest in the Macroscopic Fundamental Diagram (MFD) in the last decade, studies on network-level urban traffic control have increased in popularity. A popular urban traffic control approach is perimeter control, in which vehicle accumulation is kept below some critical accumulation value. An alternative control strategy is to optimize time series of departure rates as a means to limit inflows into the (sub)network. In this paper we test how these approaches compare in terms of minimizing total time spent (TTS), and whether network performance can be improved by combining these two approaches. To the best of the authors’ knowledge, answers to these two questions are still missing. Our findings indicate that—for a particular multi-region network under a specific demand profile—optimizing departure rates outperforms perimeter control. Particularly, we find that the combination of perimeter control and departure rates optimization may even have adverse effects on minimizing TTS, compared to optimizing departure rates only. We also show that properly over-saturating part of a network could result in less TTS than under the application of a perimeter control, which keeps the accumulation under the critical accumulation.