Provo, UT to Grand Tetons US-189 / I-80 / WY-89

The big news is that the Provo to Salt Lake corridor rebuild has been completed. That project expanded I-15 from Lehi to Spanish Fork by an additional two lanes in each direction and eliminated 24 miles of the worse bottleneck along the Wasatch Front IMO.

With the exception of occasional lane closures for maintenance, work on I-15 from Provo to Ogden is now pretty much complete.

You still have to deal with rush-hour traffic, but that's something you can plan for and avoid.