The is a national expressway in Okayama Prefecture, Japan. It is owned and operated by West Nippon Expressway Company.
The expressway is officially referred to as the Chà «goku-à Âdan Expressway Okayama Yonago Route. The Chà «goku-à Âdan Expressway Okayama Yonago Route is the official designation for the Sanyà  Expressway between Okayama Interchange and Okayama Junction, the Okayama Expressway between Okayama Junction and Hokubà  Junction, the Chà «goku Expressway between Hokubà  Junction and Ochiai Junction, and the Yonago Expressway between Ochiai Junction and Yonago Interchange (concurrent with the Chà «goku-à Âdan Expressway Okayama Yonago Route).
The first section of the expressway was opened in 1991. The final section of the expressway (41.2 km between Okayama-Sà Âja Interchange and Hokubà  Junction) was opened on March 15, 1997. The route originates from its junction with the Sanyà  Expressway and extends northward. At its northern terminus it connects to the Chà «goku Expressway.
The expressway is 4 lanes from Okayama Junction to Kayà  Interchange and the remainder is 2 lanes. The speed limit is 80 km/h on 4-laned sections and 70 km/h on 2-laned sections.