I-25 South Gap: Monument to Castle Rock

Project Facts

The Gap is an 18-mile stretch of Interstate 25 from south of Castle Rock to Monument. It is the only four-lane section of I-25, connecting Colorado's two largest cities, Denver and Colorado Springs. Over the years, congestion, crashes and delays have grown due to population growth and more people using the road.

Efforts to improve these conditions are underway.

  • Cost: $350 million, with contributions from Douglas and El Paso counties, Pikes Peak Regional Transportation Authority and a federal INFRA grant
  • Contractor: Kraemer North America
  • Timeline: September 2018-late 2021; toll testing to continue into early 2022
  • Location: 18 miles in both directions of I-25, south of Castle Rock to Monument, in Douglas and El Paso counties

Construction to Begin on I-25 South Gap

Starting in early September, crews on this project will begin making improvements to an 18-mile stretch of Interstate 25 known as "The Gap," which starts south of Castle Rock and continues to Monument. In addition to building one new lane in each direction of I-25, this project will provide the following benefits:

 Safety: Crews will widen shoulders outside and inside the travel lanes for vehicle pull-off and emergency response. This improvement will also help with drainage.

 Driver choice: After crews add an Express Lane in each direction of I-25, drivers will have the choice to use the Express Lane for a reliable trip in exchange for a variable toll, or to use one of the two general-purpose lanes for free. Carpoolers (vehicles with three or more people) can ride the Express Lane for free.

 Wildlife safety: Crews will construct five new wildlife crossings and install deer fencing.

 Improved pavement: Crews will add a new overlay to the existing pavement for a smoother ride.

 Improved infrastructure: Crews will repair or replace four bridges, and extend ramps.

 Improved truck access: Crews will add truck climbing lanes near Monument Hill and the Greenland exit.

 Advanced technology: Crews will modernize communications and power along the corridor to enable advanced technology.


Work will begin in September 2018 on the northern end of the project near Castle Rock. By summer 2019, the entire 18-mile corridor will be under construction. Overall, the project is expected to be completed in spring 2022. This will be the fastest CDOT has ever delivered a project of this size.

Driver Impacts

Construction, by nature, will always impact those who use the road. Two lanes of traffic will be maintained in each direction during the day.

Still, drivers should expect slower speed limits (65 mph), narrower lanes, increased volume, nighttime lane closures, and construction trucks entering and exiting the interstate throughout the corridor.

Construction crews will be working around-the-clock and sometimes on weekends to deliver these improvements on-time, on-budget and with as little impact as possible.

Open Houses 

Learn more about construction at one of two open houses:

  • For El Paso County
    5-7 p.m.
    Monday, Aug. 20
    Monument Academy
    1150 Village Ridge Point
  • For Douglas County
    5-7 p.m.
    Wednesday, Aug. 22
    Douglas County Fairground
    500 Fairgrounds Road
    Castle Rock

Telephone Town Hall 

  • 6:15-7:15 p.m.
    Thursday, Sept. 6

Our automated system will call some area stakeholders. If you don't get a call and want to participate, call 1-877-229-8493, and enter passcode 117409.

Contact Us


Colorado: The Official State Web Portal