System Optimum Diversion of Congested Freeway Traffic

We study the system optimum dynamic traffic assignment (SODTA) in a network consisting of a freeway and neighboring city streets. There is only one bottleneck in the freeway and every destination is somewhere downstream of the bottleneck. Vehicles can be diverted through off-ramps leading to alternative local street routes. We formulate the problem and determine a graphical solution procedure based on Newell's cumulative plots, which yields the optimal diverted flow over time. On-ramps can be conveniently incorporated in this procedure yielding SO metering rates. The following variants are considered: capacitated and uncapacitated off-ramps, and deterministic and stochastic demand.