  During the pandemic of COVID-19, the demand of the transportation systems are
drastically changed both qualitatively and quantitatively and the network has
become obsolete. In this article, we study the problem of finding an optimal
subnetwork that guarantee that (i) the minimal access time from any node of the
urban network to the new network is not {\em too large} compared to the
original transportation network; (ii) for any itinerary, the delay caused by
the deletion of nodes of the transportation network is not {\em too big}; and
(iii) the number of nodes of the transportation network has been reduced at
least by a known factor. A solution is optimal if it induces a minimal global
delay. We model this problem as a Mixed Integer Linear Program before applying
the model on a real-case application on the Lyon's buses transportation
network.
