Prior to 1977 Utah used a system where every U.S. Highway and Interstate Highway traversing the state was assigned a different Utah state route number.
There were many instances where having different route numbers for signing and legislative purposes could cause confusion.
[1] In 1977, the state changed to a system where all highways would have the same legislative route number as its signed route number.
The other routes in the overlap would have a discontinuity in the legislative description.
For example, the stretch of highway between Green River and Crescent Junction is legislatively designated only Interstate 70.