The transportation system is less variable than settlement patterns or the allocation of economic activity. This necessitates checking the optimality of spending on the development of transportation networks. Previous work in this area proposed criteria for the optimal development of transport networks for a single mode of transportation. The study demonstrates how, with the help of carrying capacity, a multilayer network can be “collapsed” to a representation convenient for working with the usual tools of spatial general equilibrium models. The possibilities of the new approach have been tested on the example of the Kaliningrad oblast. It was found that the distribution of the carrying capacity between the urban districts of the Kaliningrad region is not optimal: the carrying capacity of the roads in the latitudinal direction is insufficient. It follows from the model that new investments in road construction should bring the carrying capacity of roads between municipalities closer to such levels that the ratios of carrying capacity between pairs of adjacent territories correspond to those in the model with a zero lower limit of the optimal carrying capacity value.