It’s a weekday morning and traffic appears a bit lighter than usual along a section of highway between Denver and Castle Rock.

But it’s not Interstate 25. A $100 million infrastructure project has expanded a section of U.S. 85, or Santa Fe Drive, in northwest Douglas County through Highlands Ranch.

The largest transportation project in the county’s history finished three months ahead of schedule, officials said.

Reconstruction expanded the number of lanes between Highlands Ranch Parkway and Dad Clark Gulch north of County Line Road – a corridor county officials dubbed as “one of the busiest and fastest-growing corridors in Douglas County.”

The stretch of road serves approximately 25,000 motorists a day between Denver and Castle Rock in central Douglas County, according to roadway studies cited by the county.

Officials anticipate the corridor will double in roadway activity by 2040.

Improvements “were designed to enhance safety, reduce congestion, and support future growth along the corridor,” officials said in a statement.

On Wednesday, Douglas County officials, joined by those of Highlands Ranch and the Colorado Department of Transportation, celebrated the completion of work three years after groundbreaking.

“It’s not just the county’s largest transportation project ever, it’s a big moment for our community and its families – all ahead of schedule,” Commissioner Kevin Van Winkle, who represents Highlands Ranch, told The Denver Gazette in a statement.

“As someone who grew up in Highlands Ranch,” he said, “I know how significant these improvements are for our residents.”

A county spokesperson said the project was scheduled to finish in October.

Three years ago, Douglas County partnered on the $100 million infrastructure project with the Federal Highway Administration and CDOT.

Their focus? To transform what is criticized as a congested, two-lane highway into a modern, four-lane divided expressway.

Santa Fe Drive between Highlands Ranch Parkway and County Line Road also crosses over C-470, which received a lot of attention during reconstruction. Here’s a breakdown of what received improvements:

• Widening U.S. 85 with an additional lane in each direction, plus new auxiliary lanes, all repaved.
• New wide bridge over C-470 with updated on-and-off ramps.
• Three new continuous flow intersections at Highlands Ranch Parkway, Town Center Drive and C-470.
• Over 2.5 miles of new pedestrian and cyclist paths from north of C-470 to Highlands Ranch Parkway.
• Two new grade-separated trail underpasses under C-470 and High Line Canal Trails, providing access to hikers and bikers.
• New roadway pavement and permanent safety medians throughout the corridor.
• Seven improved Regional Transportation District bus stops.
• Signal replacements/updates with timing adjustments.’
• Major utility relocations and storm water drainage improvements.

Officials warned motorists that crews may be in the area through the fall to monitor environmental growth and finish minor touch ups.

“This is the largest transportation investment in Douglas County history,” Commissioner Abe Laydon told The Denver Gazette. “It’s more than just moving cars, it’s about moving lives forward. Families will spend less time in traffic and more time together with safer commutes.”