System optimum dynamic traffic assignment graphical solution method for a congested freeway and one destination

This paper studies the system optimum dynamic traffic assignment in a network consisting of a hypothetical surface street grid and a congested freeway section. Vehicles can be diverted through off-ramps, and on-ramps can be metered. The family of solutions are identified graphically using Newell’s queueing diagrams. Because enforcing diversion is still a technological puzzle, these results provide a benchmark for future ITS applications, and a building-block for including both departure time choice and several destinations. It is also shown that pricing according to marginal cost would be difficult to implement in this case, that eliminating all queues from the freeway is always suboptimal, and that ramps near the bottleneck should be metered more severely.