I-25 South Gap: Monument to Castle Rock

I-25 South Gap Logo

About the Project

Construction on the 18-mile South Gap project to improve safety and travel reliability began in September 2018. The I-25 South Gap is Colorado's longest construction zone. 

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: $419 million, with contributions from Douglas and El Paso counties, Pikes Peak Rural Transportation Authority and a federal INFRA grant (scroll down for details)
  • Contractor: Kraemer North America
  • Timeline:  Construction began in September 2018 and completed in November 2022
  • Location: 18 miles in both directions of I-25, south of Castle Rock to Monument, in Douglas and El Paso counties

Project Benefits

The I-25 South Gap: Monument to Castle Rock project delivered:

 Increased Safety: Wider shoulders allow room for vehicle pull-off and emergency response. This improvement also helps with drainage.

 Driver choice: The addition of an Express Lane in each direction of I-25 gives motorists the choice to use the Express Lane for a reliable trip in exchange for a toll or to use one of the two general-purpose lanes for free. Carpoolers (vehicles with three or more people) and motorcyclists can ride the Express Lanes for free.

 Wildlife safety: Four new wildlife crossings and 28 miles of deer fencing are anticipated to help decrease animal-vehicle collisions by 90 percent.

 Improved pavement: A new asphalt overlay to the existing pavement provides a smoother ride.

 Improved infrastructure: Reconstruction of five aging bridges and the extension of on- and off-ramps for improved operations.

 Improved truck access and safety: Implementation of truck climbing lanes near Monument Hill and the Greenland exit allow slower moving vehicles to stay to the right. A new truck chain-up station along southbound I-25 in Larkspur allows drivers to safely chain up in inclement weather before the climb over Monument Hill.

 Advanced technology:Modernization of communications and power along the corridor to enable advanced technology.

Tolling Information

Express Lanes tolls along I-25 between Monument and Castle Rock are currently waived during the tolling testing period. Toll commencement is anticipated in 2023.



Gap Map Horizontal view of Stretch.