Mountain road conditions can change in the blink of an eye. During the summer, a sudden downpour can generate mudslides or even deposit giant boulders onto the roadway. Rain can turn to ice, and blizzard conditions can hit with little notice. Those road conditions – along with maintenance activities and construction – can delay traffic and cause accidents.

A 2011 CDOT speed study revealed that traffic throughout the Glenwood Canyon Corridor demonstrated a speed differential of approximately 10 mph between passenger vehicles and commercial vehicles. Considering the grades and curves through Glenwood Canyon, CDOT determined 50 mph as a safe speed for commercial vehicles greater than 26,000 GVWR and 60 mph for cars. When there is an accident, adverse weather conditions, or construction, CDOT lowers the speed limits, keeping passenger and commercial vehicle speed limits the same.