The Colorado Department of Transportation has released the results of the first phase Feasibility Study, which found that a reversible lane on Interstate 70 in the mountains is geometrically feasible and if implemented in the eastbound direction, could reduce travel time by about half in this direction.


However, the study also found that this would double travel time for westbound travelers and that westbound traffic is too heavy to implement a reversible lane in the eastbound direction in the summer.

This "zipper lane or reversible lane" is a highway lane that can reverse direction during peak travel times to better manage traffic. It would stretch from eastbound I-70 west of Empire Junction and continue to the base of Floyd Hill, a total project length of about 15 miles.

Adding a reversible lane in the westbound direction would provide little benefit, the study found. Even though westbound traffic is heavy on Friday afternoons and Saturday mornings, the highway is not at capacity for enough time to open the lane, which can take up to 1.5 hours to change direction. Therefore, if a reversible lane were to be implemented on I-70, it would be used only for eastbound traffic during the ski season on Sundays.

"While reversible lanes have been used with success in several states, they have not been used under the challenging conditions presented on the I-70 west mountain corridor," said Tony DeVito, CDOT region 1 director. "We know of no cases where zipper lanes have been used for such a long stretch of highway with no access in or out on a corridor with extreme weather and leaving only one lane on an Interstate highway. We are encouraged about the prospect of this project but we are proceeding cautiously to assure it provides a safe short-term solution to traffic without causing unacceptable problems for those traveling in the opposite direction or for the local communities."

This first phase Feasibility Study was conducted by the University of Arizona and the University of Colorado at Denver to take a very high-level look at the feasibility of implementing this lane under normal conditions. The primary purpose of the study was to assess what the impacts to westbound traffic would be if the highway was reduced to just one lane in this direction. It analyzed and simulated traffic operations based on collected traffic data for 236 Sundays between January 2004 and March 2010. However, it did not take into consideration inclement weather or incidents specifically.

CDOT is in the process of proceeding with the second phase of the study, working with stakeholders along I-70 to examine issues like snow removal, emergency response, wildlife, modes of operations and other environmental issues and concerns about access to local communities. CDOT plans to complete this phase by early 2011. If it is found to be safe, affordable and feasible, the system could be implemented in the 2011/2012 ski season. Policy and operational issues have not yet been discussed, nor has a method of funding the system. The system could cost between $30 and $35 million.