 I-25 briefly parallels US 87, US 20, and US 26 (Yellowstone Highway) and enters the city of Casper at a complex junction—the complexity is explained in the description for I-25 Bus.—where the Interstate crosses over Yellowstone Highway, the three U.S.Highways join I-25, I-25 Bus.splits from the Interstate to serve downtown Casper, and US 87 Bus., US 20 Bus., and US 26 Bus.