According to the technical grade, China's highways are divided into five grades: expressway, first-class highway, second-class highway, third-class highway and fourth-class highway. Among them, other highways other than expressways are called ordinary highways.

According to the administrative grade, highways are divided into six grades: national highway, provincial highway, county road, township road, village road and special highway. Among them, national highways include national highways and ordinary national highways, and provincial highways include provincial highways and ordinary provincial highways.

National Highway 3 15 starts from Xining, Qinghai and ends in Kashgar, Xinjiang, with a total length of 3,063 kilometers.

Highway G3 15 extends along the east-west direction of Kunlun Mountain, passing through Hotan and Milan ruins, passing through Lop Nur Wild Camel Nature Reserve, passing through Altun Mountain, one of the four uninhabited areas in China, passing through Qaidam Basin, bypassing Qinghai Lake, and taking you to appreciate the cultural relics and historic sites in Xinjiang.

The 3 15 national highway, which runs through no man's land in Qaidam, is comparable to route 66 in the United States. The yellow sand is vast and the Gobi is endless. Plateau, lakes, snow-capped mountains and Gobi are all silent, lonely, broad, desolate and magnificent.

Refer to the above? Baidu Encyclopedia 3 15 National Highway