Found this at
http://www.koyagi.com/ACPages/ACmain.html
The name of the Eastern Sea Road was the Tokaido road. It ran mostly
along the Pacific coast and has been around since before they thought
to keep track of history in Japan. It said there were 53 shukuba
machi along the route. These were posting stations were travelers
rested and were controlled by the Bakufu. Remember, they did this to
keep track of potential threats to the Shogun. The road is mostly
covered by the Tokaido highway now, but you can still see parts of
the old road today and the Shinkansen line is supposed to run more or
less alongside the old route.
Apparently it was one of five Gokaido or main highways during the Edo
period. The site listed one other route. The Nakasendo road was about
500km or 310 miles long and had 67 shukuba machi. It began in
Nihonbashi in Edo and ended in Kyoto, cutting through the mountainous
central region of Japan. Because it was a much harder way, it was
less travelled than the Tokaido road.