Roads

If you are starting from Salt Lake City, the elevation will be higher there, around 4200 feet, going down to about 2000 feet in Las Vegas.

The route along I-15 will go up first, peaking around 6500 feet close to Fishlake National Forest, before heading back down quickly as you pass Zion National Park.

Hopefully someone who's done this exact trip can tell you more about how it feels. I'm not sure if there is any alternative route that would be flat, since this is the main route most people would take.

My husband and I have driven this route several times in the winter pulling a 5th-wheel and it was really easy. You do drop a lot from Saint George to Mesquite but it’s a good freeway.

This is a terrible city to drive in on the Interstate. Call the hotel ahead and get exact best route. High speeds. Be safe.

I did from Salt Lake City to Reno and on to Sacramento in a 1932 Plymouth where we did not want to climb mountains. (This was back in the 60s).  I do not remember much mountainous between SLC and Reno, but coming down into Sacramento was very steep (although not scary). 

I have done this route several times, and the only spot that makes me nervous is when you pass into the corner of Arizona from Utah, you go through a canyon, so its windy roads. So I just stay in the right lane and take my time.