Off-Ramp Coupling Conditions Devoid of Spurious Blocking and Re-Routing:

When modeling vehicular traffic flow on highway networks via macroscopic models, suitable coupling conditions at the network nodes are crucial. Frequently, the evolution of traffic flow on each network edge is described in a lane-averaged fashion using a single-class Lighthill-Whitham-Richards model. At off-ramps, split ratios (i.e., what percentage of traffic exits the highway) are prescribed that can be drawn from historical data. In this situation, classic FIFO coupling conditions yield unrealistic results, in that a clogged off-ramp yields zero flux through the node. As a remedy, non-FIFO conditions have been proposed. However, as we demonstrate here, those lead to spurious re-routing of vehicles. A new coupling model, FIFO with queue (FIFOQ), is presented which preserves the desirable properties of non-FIFO models while not leading to any spurious re-routing.