Denver International Airport is 220 miles from Aspen and approximately 4 hours by car in good weather and considerably longer in snowy conditions. The route follows Interstate 70 except for 42 miles on the four-lane State Highway 82 between Glenwood Springs and Aspen. The route along I-70 has some 7% grade inclines and declines and the road from Glenwood Springs to Aspen can be very icy in spots. If you are not experienced driving in the mountains in winter, you may want to consider an alternate mode of transportation.
The Colorado Department of Highways website has real time conditions and web cams along the route from Aspen to Denver.