御堂筋線
In 1964, the portion of the route between Kita-ku and Osaka Prefecture Route 9, known as the Shinmidō-suji, was built alongside the extended Midōsuji Line to accommodate automobile traffic from Shin-Ōsaka Station into central Osaka. Later in the decade, Shinmidō-suji was extended north again along with the Midōsuji Line to Suita were the venue for the Expo '70 was. National Route 423 was established in 1982 along the Shinmidō-suji, the planned Minō Toll Road, and the older Settan-kaido.