There's really no alternative to driving. Motorists should be aware that the eastern side of this region contains some seriously high passes, particularly Wolf Creek Pass on US 160 as it crosses the Continental Divide, and Coal Bank Pass, Molas Pass, and Red Mountain Pass on US 550 the "Million Dollar Highway" between Durango and Silverton. These are commonly closed for periods of time during the winter. There are even "avalanche tunnels" along some of the routes, to prevent your car from being swept off the road into deep ravines by falling blocks of snow. The western part of the region is lower and less prone to road closures, but towns with gas stations and services are few and far between.
During the winter, heavy ice and snow are a major concern, which can make driving difficult and slow going. Always check the weather and road conditions (http://www.cotrip.org) before heading out. Even on a clear winter's day, make sure your vehicle's wiper fluid reservoir is full. The Colorado Department of Transportation CDOT (http://www.dot.state.co.us) spreads both sand and magnesium chloride on the roads, which makes for an impenetrable, gluey mess on your windshield.
In the summer months, it's not uncommon to see the shoulders of the highways littered with broken-down vehicles that could not handle the steep grades and high altitude air of the Rocky Mountains. If you are venturing from a lower altitude, make sure your car can handle mountain driving. Thinner air means you will be burning more gasoline. Also, with so many steep grades, expect to gear down to avoid unnecessary friction to your brake pads.
