Dynamic Traffic Assignment in Design and Evaluation of High-Occupancy Toll Lanes

Application of a dynamic traffic assignment-simulation methodology to the analysis and evaluation of network performance under various schemes for the design and operation of high-occupancy toll (HOT) lanes is described. The DYNASMART traffic simulation-assignment model, which combines the ability to simulate traffic flow and to represent dynamic route choice behavior, is used to model the problem. Different dimensions for the design and operation of HOT lanes are considered in this study, including ( a) lane utilization in terms of adding a new lane or using an existing lane of the facility as a HOT lane; ( b) physical separation of the HOT lane in terms of access point frequency; ( c) access restriction based on vehicle occupancy; ( d) HOT lane pricing structure, which may be fixed or congestion dependent; and ( e) different demand levels with different percentages of high-occupancy vehicles (HOV). A set of experiments was designed to compare the performance of the HOT lanes and the total network under these different operating characteristics. A network in Texas that represents the south central part of the Fort Worth area is used in these experiments. The results were analyzed under each of these different operating characteristics, yielding useful insights for the design and evaluation of HOT lanes.