A bottleneck model for bidirectional transport controlled by fluctuations

The authors introduce a new model to study the oscillations of opposite flows sharing a common bottleneck and moving on two totally asymmetric simple exclusion process (TASEP) lanes. They provide a theoretical analysis of the phase diagram, valid when the flow in the bottleneck is dominated by local stationary states. In particular, they predict and find an inhomogeneous high-density phase, with a striped spatio-temporal structure. At the same time, their results also show that some other features of the model cannot be explained by the stationarity hypothesis and require consideration of the transients in the bottleneck at each reversal of the flow. In particular, the authors show that for short bottlenecks, the capacity of the system is at least as high as for unidirectional flow, in spite of having to empty the bottleneck at each reversal -- a feature that can be explained only by efficient transients.