I'm guessing it will really depend on the breakdown between city and territorial governments. One can easily imagine that the city guards will patrol the road out of town for a certain distance but that roads which do not go to any town but merely between other roads would be the responsibility of the territorial government so that there might be an outpost on the road but the patrols would be infrequent depending on the importance of the road. It might even be that the guards in the outpost would charge an unofficial toll when possible.