Real-time congestion pricing strategies for toll facilities

• Total system delay can be minimized with many different pricing strategies.
• Given an operator objective, the optimal pricing strategy can be reduced to finding a single parameter value.
• Maximum revenue under minimum total delay implies toll facility at capacity with no queues for as long as possible.
• The concept of alternative-specific marginal cost is clarified.

This paper analyzes the dynamic traffic assignment problem on a two-alternative network with one alternative subject to a dynamic pricing that responds to real-time arrivals in a system optimal way. Analytical expressions for the assignment, revenue and total delay in each alternative are derived as a function of the pricing strategy. It is found that minimum total system delay can be achieved with many different pricing strategies. This gives flexibility to operators to allocate congestion to either alternative according to their specific objective while maintaining the same minimum total system delay. Given a specific objective, the optimal pricing strategy can be determined by finding a single parameter value in the case of HOT lanes. Maximum revenue is achieved by keeping the toll facility at capacity with no queues for as long as possible. Guidelines for implementation are discussed.