The proposed Interstate 70 zipper lane, a reversible lane to help ease Sunday east-bound traffic through the mountain corridor, offers a possible short-term, relatively low-cost solution to the crippling peak-season traffic on the highway, but comes with significant trade offs and complications.
The zipper lane is expected to cut eastbound travel time in half on peak Sundays during ski season and presents a fast, less expensive solution to the congestion problem. It also carries almost no negative impacts to the environment.
However, the zipper lane is expected to double westbound travel times when in use and increase accidents.
There will also be complications when cars crash or break down while using the lane, as westbound traffic will have to be stopped to allow emergency vehicles through. Plowing the lane during heavy snow could also be problematic.
The proposed I-70 zipper lane is essentially unique. While similar lanes exist in Boston and Utah, the I-70 lane would be longer - approximately 13 miles from Georgetown to the bottom of Floyd Hill - and would run through more difficult mountainous terrain than any other state's reversible lane. Similar projects in other states also leave at least two lanes of traffic running in the usual direction while the zipper lane reverses traffic in a separate lane, which would not be possible on I-70.
Still, the project is technically possible, CDOT officials say, has no fatal flaws and will mitigate the congestion problem for the next five to 10 years, while the more permanent solutions of the preferred alternative are still in the planning stages.
"I think the view is, what can we do short term that will actually improve safety and improve capacity along the corridor?" I-70 coalition member Michael Penny said. "Because we are so far out on these other large project components."
But Clear Creek County Commissioner Kevin O'Malley said the zipper lane -which will only be open approximately 17 days a year - might not be worth the at least $23 million it is expected to cost.
He said the funds would better spent on other corridor projects, such as the twin tunnels, which will continue to be a problem for traffic even if the zipper-lane plan is implemented.
"What we are in favor of is directing whatever resources might be available toward designing and building a solution for the Twin Tunnels," O'Malley said. "You're not really solving anything until you solve that bottleneck."
Funding continues to be a big question on the project. The phase two study recently released by CDOT addresses the possibility of road tolls for all east- bound lanes while the zipper lane is open, but getting a toll approved would be difficult and in the end, road fees would bring in only between $200,000 and $750,000 per year.
The study states simply that, "there are several federal and state funding sources that could provide funding," but that "priorities would need to be reallocated ..."
Members of the I-70 coalition would like to see the project funded by new dollars so that it didn't take money from other projects in the corridor.
But Penny said the plan, whether it is successful or not, is only one of dozens of possible short-term solutions to the congestion problem.
An alternative to the zipper lane would be using the shoulder space on the eastbound lanes to create a third lane during peak times. However, the shoulder solution would work only up to the Twin Tunnels, where there is no road space to create an extra lane.
Other possible solutions include collaboration between CDOT and the trucking industry, to arrange for deliveries to be made at slower times, as well as the ski industry to encourage visitors to leave later on Sunday afternoons.