Analytical Capacity Comparison of One-Way and Two-Way Signalized Street Networks

Abstract

Recently cities have been converting traditional one-way downtown street networks to two-way operation partly because one-way networks are seen as confusing and as less conducive to economic activity and a livable environment and they require vehicles to travel longer distances on average. However, one of the main disadvantages of such conversions is thought to be a reduction in the network's ability to serve vehicles. Intersections in two-way networks can serve fewer vehicles per unit time than their one-way counterparts. Several studies have assessed the differences between these two types of networks, but most studies are site specific and do not consider the best possible two-way networks. This paper presents an analytical model that uses macroscopic analysis techniques to compare various one-way and two-way networks using their trip-serving capacities. This metric is a key indicator of network performance. Two-way networks can serve more trips per unit time than one-way networks when average trip lengths are short. This study also found that two-way networks in which left-turn movements were banned at intersections could always serve trips at a higher rate than one-way networks could, even long trips. Thus, the trip-serving capacity of a one-way network can actually be increased when it is converted to two-way operation if left turns are banned. In this way, livability and efficiency objectives can be achieved simultaneously. This framework can be used by planners and engineers to determine how much a network's capacity changes after a conversion, and also to unveil superior conversion options.