Construction launches Monday on a westbound toll lane on Interstate 70 from the Veterans Memorial Tunnels in Idaho Springs to Empire Junction, part of Colorado transportation officials’ latest effort to ease congestion on the heavily traveled roadway.

Gov. Jared Polis is expected to join a groundbreaking ceremony Thursday to kick off the $70 million project that is set to be complete in the spring of 2021. That means mountain motorists can expect to see crews at work in the area for at least the next two ski seasons.

The initiative aims to build off what the Colorado Department of Transportation says are the successes of the eastbound Mountain Express Lane in the same stretch that has been open since 2015.

The roadwork to complete the eastbound toll lane caused some headaches for motorists and businesses in Clear Creek County that CDOT says will inform this project.

“There is a better understanding of how the interstate operates so the lessons learned can be applied with what we are doing with the westbound side,” said Tamara Rollison, a CDOT spokeswoman.

Here’s what you need to know about the project as it gets going:

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How will the lane work?

The lane will operate the same way the eastbound toll lane functions now.

That means it can be open for only 100 days a year, limited mostly to holidays and weekends. The toll drivers will be charged will go up and down depending on the volume of traffic. When it’s not in use, the lane will be a shoulder.

In the eastbound lanes, that’s typically $5 to $7 for vehicles equipped with an ExpressToll transponder, although the Mountain Express Lane toll can get as high as $30 under CDOT’s fee scheme. Tolls are higher without the transponder. You can get a transponder here.

Interstate 70 ski traffic in Clear Creek County in February 2019. (Nathan Hahn. Special to The Colorado Sun)

Rollison said CDOT won’t know exactly what the westbound toll lane fees will be until later in the construction process. “We’re not going to know precisely what that’s going to be until” closer to the opening, she said.

At 12 miles, the westbound toll lane will be slightly shorter than the existing eastbound lane at 13 miles.

You might be asking why the lane has to be tolled. CDOT has used toll lanes as a way to cover the cost of several different projects across the state, including on Interstate 25 and U.S. 36 between Denver and Boulder.

MORE: “It’s nightmarish”: Colorado faces meager budget in fight against I-70 ski traffic

Is the eastbound toll lane working?

Yes, according to CDOT. It has improved traffic flows overall.

“We have found that we have improved travel times by as much as 52% during busy holiday travel times,” Rollison said. “So we definitely have seen an improvement in traffic flows during the highly congested periods. We expect to have the same kind of success on the westbound side, too.”

The 52% reduction in travel time translates to more than 20 minutes, including for people not actually traveling in the toll lane, CDOT says.

CDOT says it has taken in over $5.7 million in gross revenue from the eastbound toll lane, money that has been reinvested back into the corridor. The 2019 fiscal year saw the greatest revenue, at nearly $2 million.

For some perspective on how many vehicles travel the route: this year 5.35 million cars passed through the Eisenhower-Johnson Memorial Tunnels between November and March. That was just shy of the four-month record of 5.61 million vehicles set in 2017-18.

MORE: Heavy snow led to a top-five Colorado ski season and a whole lot of cars through the I-70 tunnels

What can I expect as a motorist?

CDOT says it is working hard to make sure that impacts to motorists and surrounding businesses — including recreation destinations, like ski areas — will be minimal.

“We have studied this concept for quite a bit,” Rollison said. “We have had a number of community and town meetings along the corridor.”

Rollison said the agency is aiming to make a big communications push to motorists so they are aware of the construction. Westbound travel will remain open during construction, and any lane closures are slated to happen only at night, she said.

Still the area will be a construction zone with signs reminding motorists to slow down and everything else you might expect with roadwork.

What else is CDOT doing to fix I-70?

The westbound Mountain Express Lane is just part of CDOT’s broader plans for easing congestion on I-70 through the high country, but the hiccup remains funding.

The next big project transportation officials are eyeing is a major overhaul of the Floyd Hill interchange, where I-70 meets U.S. 6 at Clear Creek Canyon. That project, which includes plans for a tunnel and lane widening, has an estimated price tag of some $500 million.

“We don’t have the funding identified to make those improvements,” Rollison said.

To put the cost of the Floyd Hill project in context: The toll lane construction on an 18-mile stretch of Interstate 25 between Monument and Colorado Springs was budgeted at $350 million.

There are also a number of smaller projects being worked on along the I-70 mountain corridor.

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