On the substitutability of traffic light and pricing controllers in transportation networks

Abstract

The maximum level of performance reachable by traffic control policies is directly affected by the locations and types of controllers employed in the network. We therefore investigate methods to identify locations and types of controllers that guarantee that the highest possible level of performance can be reached, fully exploiting the available network capacity, while minimizing the overall installation costs. This condition is known as full controllability. In this work, based on an existing methodological contribution that allows to determine the optimal number and locations of Pricing controllers required to reach the maximal level of controllability in transportation networks, we investigate instances and conditions in which the same results can be achieved through Traffic Light controllers, which represent a more realistic and widespread technology. Due to the different impact of traffic lights and pricing controllers on the network, however, optimal locations for one set might differ from the optimal locations for the other. Consequently, replacing pricing controllers by traffic lights is not a straightforward task. Moreover, an enumeration of every possible combination of traffic light positions will result in combinatorial explosion. In order to avoid this problematic, in this work we study simple, atomic subnetwork structures, widely occurring in real-life networks, and assess whether it is possible to maintain the maximum level of controllability while replacing pricing controllers with traffic light controllers. We validated our approach on a set of increasing sized networks showcasing that our proposed substitution rule yields satisfactory results in more than 90 percents of instances. This first empirical step acts as the basis to study larger and more realistic transportation networks, therefore helping to develop a general methodology to substitute pricing controllers with traffic lights.