Transportation planners are unveiling an ambitious blueprint to unsnarl traffic jams in Denver’s western suburbs — one that could more than double the size of C-470 near Morrison, expand Highway 93 south of Boulder to four lanes and, along the beltway, embrace the future of self-driving vehicles with a first-in-the-state lane designation for their use.

That strategy — the more expansive of two approaches the state is considering — is a response to projections of mushrooming traffic along those major arteries over the next two decades and comes on the heels of announcements from automotive giants about autonomous-vehicle rollouts as soon as next year.

But as with all large road-improvement projects in Colorado, how much of that vision becomes reality and when will depend on funding — improvements to the 26-mile stretch encompassing C-470, Highway 93 from Littleton to Boulder and U.S. 6 could cost anywhere from $1 billion to $2 billion.

“It’s all about the money,” Colorado Department of Transportation spokeswoman Amy Ford said.

CDOT’s budget is notoriously constrained, with the agency estimating last year that it will incur a funding shortfall of $9 billion over the next decade if new money can’t be found. The western suburbs will have to compete with several other corridors in the Denver metro area when it comes to transportation dollars, including the $276 million expansion of the eastern segment of C-470 through Highlands Ranch.

“What is the highest priority in the region?” asked Paul Jesaitis, CDOT’s transportation director in the metro area. “Where are the most accidents? Where are the most fatalities?”

Money or no money, the need for additional lanes along C-470, U.S. 6 and Highway 93 is indisputable if projections for traffic growth in the corridor are to be believed.

According to data from the Denver Council of Regional Governments, average daily weekday vehicle counts will grow from just under 70,000 at C-470/Bowles Avenue today to more than 106,000 by 2040. Just a few miles up the highway, at Alameda Parkway, that number jumps to more than 136,000 vehicles a day in 2040 from 89,000 today.

On Highway 93 in Arvada, traffic counts are expected to leap from 25,300 vehicles daily to more than 33,000 over the next two decades, according to the council. All those numbers assume the completion of the Jefferson Parkway, a proposed 10-mile tollway that would connect Broomfield to Golden.

“When you talk about adding 50 percent to what is already causing traffic jams, people start looking for new routes,” Jesaitis said, noting that C-470 is already a pain to drive during peak hours. “They divert from their regular travel pattern and look for their next best option.”

To handle that expected volume and keep motorists from clogging local arterial roads, CDOT and the WestConnect Corridor Coalition have outlined a series of proposals and alternatives — first introduced to the public at an open house last week — that would add significant capacity to the major highways that run through the western suburbs.

The most ambitious of these would turn C-470 into a 10-lane highway just south of Interstate 70, with the likelihood those lanes would be a mix of free-to-use general purpose lanes and tolled managed lanes, like those that exist on U.S. 36. Autonomous vehicles could eventually get a designated lane to ferry their non-driving passengers up and down C-470.

Highway expansion plans take shape for western suburbs

CDOT and the WestConnect Coalition have put together proposals for expanding capacity on C-470, U.S. 6 and Highway 93 between Littleton and Boulder. This map shows the most aggressive alternative under consideration, though there is a proposal with fewer lanes along the 26-mile stretch that is also on the table. Click map marker for details

Source: Colorado Dept. of Transportation

CDOT’s manager for the project, Ben Davis, said this is the first time the agency has included the prospect of self-driving cars in one of its formal planning documents. Exactly how those vehicles would be integrated into C-470’s traffic flow is still uncertain, but Davis said they would probably start out using the existing lanes before more widespread adoption of the technology merits a lane of their own.

“This concept assumes vehicle technology will continue to evolve that would allow vehicles to travel in a specified lane to maximize the technological benefits of autonomous vehicles,” he said.

Jesaitis said planning for advanced technology on Colorado roadways is “CDOT’s responsibility.”

“We’re obligated to be thinking about this technology,” he said.

CDOT’s autonomous vehicle lane proposal is emerging as automotive giants cement plans to introduce cars that could fill them. General Motors said earlier this month it intends to introduce next year its first production-ready vehicle built with no steering wheel, pedals or manual controls. Ford Motor Company has similar plans, slated for 2021.

And Colorado is not alone in preparing for their arrival. According to news reports, transportation planners in Wisconsin are considering designated lanes along a stretch of Interstate 94 and there’s a similar proposal for Interstate 5 through Seattle.

While transportation officials in Colorado will have to figure out how to incorporate self-driving cars on existing roadways sooner than later, that is only one element of the overall roadway expansion effort on the west side of Denver. And there isn’t necessarily consensus over how big that expansion needs to be.

Golden public works director Dan Hartman, who is a member of WestConnect, a transportation coalition made up local government officials that formed in 2015, is keeping his eye on the project’s middle segment through Golden. He is not worried that a dramatically expanded C-470 would funnel excessive traffic into the city, given that traffic modeling shows most drivers peeling off on to I-70 before entering Golden.

The existing four lanes on U.S. 6 should serve Golden well through at least 2040, Hartman said, though there is room to add another lane in each direction if needed. Plenty of open space and protected land exists along Highway 93 to the north — highlighted by the 6,000-acre Rocky Flats National Wildlife Refuge — where residential and commercial development is prohibited, he said.

“We don’t see a huge amount of traffic growth north of Golden to Boulder,” he said.

Boulder County transportation director George Gerstle agreed that even if the Jefferson Parkway comes online, Highway 93 probably won’t need to go to four lanes as CDOT’s most robust alternative suggests. Employing a three-lane solution on the wind-whipped road — which is one of the alternatives being considered by CDOT — would save time and money and make it more likely work moves forward more quickly.

“We think we can accomplish that by adding alternating passing lanes, widening the shoulders, improving the intersections, adding a parallel bike trail, and adding more snow fences and a wildlife underpass for migrating herds between the Rocky Flats wildlife refuge and open space to the west,” he said.

Whatever the scope of the improvements, timing for the project is still the big unknown, Jesaitis said. CDOT is now enmeshed in a “planning and environmental linkages” study, which should wrap up in the spring. Next steps would have to await funding, and Jesaitis said it is entirely possible that the corridor could be tackled in phases as money becomes available.

There are two more open houses on the project scheduled for this week, the first on Wednesday at Three Creeks Elementary School, 19486 W. 94th Ave. in Arvada, and the second on Thursday at Ken Caryl Ranch House, 7676 S. Continental Divide Road in Littleton. Both meetings start at 4:30 p.m.

Note: In the “Level 2B Alternatives – CO 93 Segment” document, option No. 3 is no longer being considered.