The road has some of the most extreme grades (i.e. steep hills) of any highway in the interstate highway system, curves a lot to meet the demands of the mountains, and is a parking lot on prime powder weekends. It is also prone to being shut down by avalanches, rock slides and snow storms. If civilization comes to an end, I-70 will be one of the first links in the interstate highway system to be rendered impassable by the forces of nature. Traffic is increasing, although I'm skeptical of the claim that:
"If no major improvements are made along the corridor to accommodate this huge growth, the travel times between Glenwood Springs to C-470 for a distance of 144 miles would be approximately 460 minutes." That's a whopping 7.6 hours, folks. "Without improvements, the duration of a trip from C-470 to Vail will go from 1 hour 38 minutes to 3 hours 52 minutes by 2025[.]"
The draft environmental impact statement for future construction on I-70 consider a number of problems to address the highway's anticipated shortcomings. In a nutshell, they consider two highway improvement options -- a six lane highway designed for a 55 mph speed limit and a six lane highway designed for a 65 mph speed limit, as well as a number of transit options from high tech rail to a dedicated bus lane to a reversible high occupancy vehicle lane (like the one on I-25 from downtown to highway 36 to Boulder). The plan claims that doing anything more than being "public transit ready" is too expensive. I'm skeptical of that conclusion and of the traffic models that assume that people will continue to prefer roads to transit even when it takes 8 hours to drive from Glenwood Springs to Golden. Read the report (the executive summary, despite it's name is more than 50 pages long and has copious illustrations), and decide for yourself.