Having lived in Colorado for many years (about 25 for each of us), Steve and I have driven many of the mountain passes often.  We have made the drive from Grand Junction, which is 20 miles from Utah, to Colorado Springs regularly and rarely saw motor homes on our favored routes. The few we saw had Colorado license plates.  These are the 6 different routes that we have driven (in order from least favorite) for transiting purposes and are described as if driving from Grand Junction.  There are a few more not listed that we’ve driven for sightseeing reasons that would take much longer and some are not paved.

• Vail Pass, elevation 10,662 feet: The entire route is on four lane interstate highways via Denver. This is our least favorite of the routes due to the high volume of traffic between Vail and Denver and Denver to Colorado Springs.  Mileage is 302. 
• Hoosier Pass, elevation 11,542:  Four lane interstate until exiting at Frisco on highway 9.  The drive between Frisco and Breckenridge is one long traffic jam in the summer and during ski season.  There are a few tight switchbacks on the west side of Hoosier Pass but nothing our 24 foot RV can’t handle.  I wouldn’t want to drive this route with a big 5th wheel or a large Class A and toad because of the traffic and switchbacks.  There are no scary drop off areas.  This is the recommended shortest route our GPS gives at 288 miles.
• Fremont Pass, elevation 11,319 feet via Copper Mountain off of I-70,  through Leadville and Buena Vista. We have taken this route once just to see what it is like and I don’t remember anything significant as far as scenery or that it was a difficult drive.  According to Wikipedia it is a level drive with just one switchback. It is the longest drive of all at about 330 miles.
• Independence Pass, elevation 12,095 feet via Glenwood Springs, Aspen, and Buena Vista is limited to vehicles 35 feet and under.  We’ve never driven this route with a motor home but the last time I drove it in 2004 traveling east to west I was glad to be on the inside lane.  The outside lane was crumbling away in areas and the drop off is drastic.  The road may have been improved since then but for now I would only drive it going east to west.  Traditionally not open until late May, Independence Pass is the most beautiful of all the passes and there’s the added bonus of seeing Aspen and Twin Lakes. Mileage is 282.
• Tennessee Pass, elevation 10,424 feet, via Minturn off of interstate 70, to Leadville and Buena Vista.  We mostly alternate between this route and Monarch Pass as both are practically a tie. The initial climb is a bit steep but not for long and there are no switchbacks.  Maybe a curve or two.  Ski Cooper area is at the top of the anti-climatic pass.  It’s almost like “what pass?”  Shortly after Ski Cooper is the western style tourist town of Leadville which claims to have the highest elevation (10,152 feet) of any incorporated city in the U.S.  However Alma, which you drive through if you take the Hoosier Pass route, has an elevation of 10,354 feet and also makes the claim.  Prior to Tulip, we had a 27 foot 5th wheel with super cab truck and drove this route with no problem. Traffic is almost non-existent.  Mileage 302.
• Monarch Pass, elevation 11,312 might have a tiny edge because there are no miles driven on any interstate highway.  Exit at highway 50 in Grand Junction and drive via Montrose, Delta, Gunnison, Johnson Village, Woodland Park.  The highway over Monarch Pass has two lanes for the ascent on both sides and no switchbacks.  Maybe one or two curves which are no big deal,  Monarch Ski Area is on the east side just a little below the pass summit.  We’ve also driven the 5th wheel on this route and occasionally see large semi-trucks.  Mileage 296.

Note:  Recommend getting fuel in Colorado Springs or Grand Junction as it’s more expensive in the mountains.  One exception:  The Western Convenience store about 4 miles east of Woodland Park right on the highway always has the cheapest gas and diesel anywhere and it’s also where several of the “Texas Seven” were caught.

Scenery along the way:

Hoosier Pass Route:  The town of Fairplay, aka South Park from the TV series.

Hoosier Pass route: View from west side of summit

Tennessee Pass Route:  The town of Minturn is rather cute and sits along a rushing river.

Tennessee Pass route:  View from Leadville.  Turquois Lake is about 6 miles west of downtown Leadville towards these mountains and has 7 campgrounds along the shore.

Monarch Pass route:  Drive goes the entire 20 mile length of Blue Mesa Reservoir, which is the largest body of water in Colorado.  This was taken in March when the lake was still frozen.

Monarch Pass route: View from the summit

All routes except Hoosier and Vail Pass:  View if you are headed west shortly before Johnson’s Corner near Buena Vista. (P.S. Overnighting allowed at Gunsmoke Travel Plaza in Johnson Village).

Independence Pass route:  This old picture was taken at the summit and is the only one I have.  This is one pass where everyone pulls over at the summit to see the beautiful views.