  A bottleneck situation in one-lane traffic-flow is typically modelled with a
constant demand of entering cars. However, in practice this demand may depend
on the density of cars in the bottleneck. The present paper studies a simple
bimodal realization of this mechanism to which we refer to as density-feedback
control (DFC): If the actual density in the bottleneck is above a certain
threshold, the reservoir density of possibly entering cars is reduced to a
different constant value. By numerical solution of the discretized viscid
Burgers equation a rich stationary phase diagram is found. In order to maximize
the flow, which is the goal of typical traffic-management strategies, we find
the optimal choice of the threshold. Analytical results are verified by
computer simulations of the microscopic TASEP with DFC.
