LAUSR

In this paper, the authors investigate equitable congestion pricing schemes for networks of heterogeneous population with respect to income level and value-of-time (VOT). Six income-based groups are introduced to categorize the entire population, where each group is assumed to have a unique VOT from a Gini-indexed VOT distribution. Two pricing schemes are under investigation and discussion: a flat toll and a VOT-based toll. The authors firstly introduce the optimization framework for obtaining the two toll schemes, which is a complex problem to solve for large-scale multimodal networks. The authors build up a mathematical model to reproduce the aggregated traffic dynamics in a bi-modal (cars and buses) urban environment and the mode choice under different congestion pricing schemes. This system model is constructed based on the Macroscopic Fundamental Diagram (MFD) model and is able to represent congestion dynamics for given demand and urban networks. While the concept of the MFD has been widely applied on the development of traffic management strategies at network scale such as perimeter flow control, the authors discuss how efficient and equitable pricing scheme can be developed with this concept. A case study is carried out in a hypothetical two-region (center-periphery structure) urban city, and a morning-peak traffic demand profile is simulated. The performances of two scenarios are tested and compared with a base scenario where no pricing is applied. The authors show that a flat toll scheme whose objective is to minimize the total travel cost (include the total travel time and the toll paid) can effectively eliminate congestion. Then the authors focus on the impacts of pricing schemes on the entire system performance and the individual groups. The results illustrate that (i) travel behavior exhibits significant differences among the user groups, such as mode shift under high prices, (ii) when applying the flat-rate pricing, users of high VOT though benefit less in time-unit savings, however they always gain more in savings of monetized cost, and (iii) all user groups may obtain equal benefit in travel cost savings, when prices are charged on a VOT base. On-going works investigate pricing schemes for distributing the collected toll to improve equity, e.g. to subsidize the users of public transport or to subsidize the low-income groups.