With the birth of the Yamato Administration in the Kinai region (the five capital provinces surrounding the ancient capitals of Nara and Kyoto), traffic routes were improved for connecting the ancient capital Kyoto and surrounding regions governed by ruling clans, as well as for traveling between regions and the harbor (tsu).
畿内にヤマト政権が誕生すると、都（京）と周囲の豪族が治めていた地域との交流や、海辺に面した港湾（津）との間を行き来するための交通路の整備が行われた。