Report on Current Developments in High-Occupancy-Toll (HOT) Lane Research
General Direction of the Field
Recent advancements in the research on high-occupancy-toll (HOT) lanes have been focused on developing more robust and adaptive dynamic pricing schemes that can operate effectively across a variety of lane-choice models and traffic conditions. The primary objectives in this area remain to ensure the maintenance of free-flow conditions in HOT lanes to enhance travel time reliability and to maximize the throughput of these lanes to minimize overall system delays.
A significant shift in the field is the move towards control-theoretic approaches that integrate dynamic pricing with real-time traffic estimation and optimization. These approaches aim to create a closed-loop system where the pricing mechanism not only responds to current traffic conditions but also anticipates future demands, thereby stabilizing the system and ensuring optimal performance. This is particularly important as HOT lanes are designed to accommodate both high-occupancy vehicles and single-occupancy vehicles (SOVs) willing to pay a toll, necessitating a flexible and adaptive pricing strategy.
Another emerging trend is the exploration of how coordinated fleets, such as those managed by autonomous vehicle operators, can influence traffic efficiency. Research in this area is examining the interplay between individual driver behavior and centralized fleet operations, particularly in terms of how fleet size impacts the overall efficiency of the transportation network. This includes studying the Price of Anarchy (PoA) in networks with varying fleet sizes, which provides insights into the potential benefits and limitations of centralized traffic management.
Noteworthy Innovations
Stable Dynamic Pricing Scheme: A novel dynamic pricing scheme has been developed that is stable and applicable to various lane-choice models with unknown parameters. This scheme employs a feedback control method to determine dynamic prices, ensuring both free-flow conditions and maximized throughput in HOT lanes.
Control Theoretic Approach: A control-theoretic approach has been introduced to simultaneously estimate the average value of time and determine dynamic prices for HOT lanes. This method guarantees the stability and convergence of the closed-loop system to an optimal state, addressing a significant gap in existing pricing strategies.
Equilibrium Dynamic Traffic Assignment Model: An equilibrium dynamic traffic assignment model with a linear programming formulation has been proposed, offering a simplified yet effective approach to finding equilibrium traffic distributions across routes and departure times. This model extends previous works by providing a solution for equilibrium problems, not just social optimum scenarios.
