The Tokugawa shogunate realized the importance of maintaining contact with distant provinces within Japan. The Tōkaidō was its most important highway.
"...Perhaps the most crucial use of the road was for governmental communication with the provinces. Official messengers traveled by foot, horseback (in wartime), and palanquin [a seat, usually for the wealthy, carried by other people]. The government used a system of relays for messengers, with reliefs at every seven li [3.9 km]. Government messengers had priority over any other type of traveler. They had first access to ferries at river crossings along the way, and could freely pass government road barriers at all times of the day or night. Private citizens were not allowed to travel at night; a series of barriers and checkpoints along the road kept them from doing so…."
What problem did the Tōkaidō address for the Tokugawa shogunate?