Denver and Colorado Springs are the top two most populated cities in the state of Colorado. Interstate 25 is the most direct and fastest way to travel between the two cities, which are 70 miles apart. This interstate is the site of the Colorado Department of Transportation’s (CDOT) longest current construction project – the I-25 South Gap.

An 18-mile stretch of I-25, the gap is the only four-lane section of I-25, with the rest of the route being at least six lanes. The road between Denver and Colorado Springs had an average daily traffic count of 80,000 vehicles in 2018, and it’s projected to reach 120,000 vehicles by 2040. Even at the 2018 usage rates, there were congestion, crashes, and delays along the route. The section that makes up the gap has not had any major improvements since the 1960s.

CDOT is adding an express lane in each direction to bring the total number of lanes to six. While the new express lanes will have tolls, vehicles with three or more people and motorcyclists can use the lanes for free. CDOT reports that drivers in both the express lanes and general-purpose lanes are enjoying increased mobility and greater trip reliability due to extra capacity.

Other project elements also contribute to the added trip reliability and provide additional benefits.

Previously, the shoulders along the road were anywhere from 6 to 8 feet. As part of the project, the inside shoulders have been widened to 15 feet and the outside shoulders are 20 feet. This improvement helps with drainage and safety as emergency responders can more easily reach those in need of help and vehicles can be pulled to the side of the road and not impede traffic flow.

A new overlay was added to the existing pavement along the entire 18-mile stretch. This will make for a smoother ride and allow drivers to maintain their speed. “The service life on the roadway expired, and the pavement was quite old and in need of improvement,” says Brock Johnson, the CDOT I-25 South Gap Project Manager who has worked in the corridor for 12 years.

The project also installed modernized communications and power along the corridor to enable new technology. The advanced technology, including message boards about travel trip time, adds certainty and helps drivers make informed decisions about their route.

Vehicles are not the only ones crossing I-25. This area also has a large animal population including elk, deer, bears, and mountain lions. Their prevalence led to an average of one wildlife-vehicle collision per day during wildlife migration seasons in fall and spring. This was an obvious safety hazard and impacted traffic flow.

Four wildlife crossings were built and 28 miles of deer fencing and several deer guards were installed. Deer don’t like walking on the deer guards, so it helps direct their movement towards safe crossings. CDOT estimates that their efforts will lead to a 90 percent reduction in wildlife incidents.

The original I-25 South Gap project had a wide scope of work. However, in 2019, the project grew when CDOT secured additional funding.

The expanded scope included the construction of the County Line Road Bridge, which is double the size of the original structure. The new structure accommodates one through lane and one turn lane in each direction, as well as shoulders on each side. The original bridge was torn down due to structural issues. Four other bridges were reconstructed, but they were part of the original scope.

I-25 runs past Monument Hill, which peaks at 7,400 feet. Slow-moving trucks often led to backups along the roadway. The project was allocated freight funds to build a southbound I-25 climbing lane and a truck chain-up station.

The chain-up station is located off the roadway in an area which was formerly a rest stop. “The station allows trucks to pull off the roadway and safely put chains on their vehicles to prepare for the climb up the hill,” says Mike Blasi, a Project Manager with Kraemer North America, which served as the general contractor on the project.

Additional funds were also used to address the issue of unsuitable soil found following the start of construction.

When construction began in September 2018, the project was slated to be complete in November 2022. Despite the massively expanded scope, the project is still running on that schedule. Not only has the team been able to keep to the original completion date, but all three lanes of traffic in their final alignment were opened to the public in December 2021 – nearly a full year earlier than anticipated.

“We kept our foot on the gas pedal and were able to do what was necessary to get the added work done on time,” Blasi says.

The fact that Kraemer could do this does not surprise Johnson. “They’re forward thinking and look for alternate ways if there are delays or issues. They can shift gears and get work done.”

Because the Construction Manager/General Contractor (CM/GC) contracting method was used, Kraemer was involved with the project earlier than typically occurs. “The CM/GC delivery method allows us to partner early on and help with scheduling, budgeting, and identifying potential issues,” says Blasi.

It also helped them stay on budget despite the great price increase of construction materials. “We got ahead of material delivery and had everything secured, except for the bridge and climbing lane, before prices surged,” says Blasi.

The $419 million I-25 South Gap project is nearly complete. The project provides greater mobility through the corridor, improves safety, and allows first responders to respond more quickly. Traveling along I-25 between Colorado’s two biggest cities has gotten a whole lot better.