  We consider a given region $\Omega$ where the traffic flows according to two
regimes: in a region $C$ we have a low congestion, where in the remaining part
$\Omega\setminus C$ the congestion is higher. The two congestion functions
$H_1$ and $H_2$ are given, but the region $C$ has to be determined in an
optimal way in order to minimize the total transportation cost. Various
penalization terms on $C$ are considered and some numerical computations are
shown.
