Back when Interstate routes were being decided in Colorado the fight was the US 6 route with a tunnel(s) or US 40 with a tunnel. The ski resorts, especially Aspen, favored US 6 which won out. Unfortunately that meant building a highway above Georgetown then through Glenwood Canyon and DeBeque Canyon, home to some of the most unstable rock to be found in the state. A tunnel under the Continental Divide on the US 40 route was feasible with known risks thanks to the Moffat Tunnel and another tunnel pushed through by the GODDAMNDENVERWATERBOARD (yes, one word to the Western Slope residents).
The point of the preceding paragraph is this; Glenwood Canyon is closed once again due to mammoth rock falls. This is almost a yearly occurrence. The Interstate has been closed for a week with no opening in sight. Once it does open many weeks will pass before it is more than one lane for both directions with pilot cars.
Bitch of a detour. Rifle to Craig on Colorado 13, all two lanes with few places to pass. At this time of year the area has huge deer and elk populations crossing the road. From Craig it is US 40 via Steamboat Springs. East of Steamboat Springs you can decide to take Colorado 131 through Oak Creek, Phippsburg, Yampa, Toponas, McCoy and Bond to Wolcott Junction and back on Interstate 70, about a 113 mile detour. Or you can stay on US 40 and join Interstate 70 below Georgetown. You have the thrill of Rabbits Ears Pass, Muddy Pass, and Berthoud Pass. This route also has eight miles of Byers Canyon West of Hot Sulphur Springs, a 35 mph two lane, no guardrails, section of US 40. While large rock falls are rare, small ones are frequent. Nasty little surprise for you as you exit one of the sharp corners.
None of the roads on this detour are adequate for heavy traffic. Many drivers have never faced these kinds of roads, especially in winter. While paved, most have no shoulders and follow what were stage coach routes. All the small towns have 25 mph speed limits. The two big towns, Craig and Steamboat Springs, have never mastered synchronized traffic signals.
If your travel plans are to/from Las Vegas or Southern California, this would be a good time to see Arizona and New Mexico. To the North, Interstate 80 is your best option.