Happy Canyon Road and Lagae Road Intersection

Project Overview

One of the 2024 Road Solutions projects, is the construction of improvements to the Lagae Road and Happy Canyon Road intersection. Project improvements will include:

    • A roundabout at the intersection of Lagae Road and Happy Canyon Road
    • Safety and traffic flow efficiency improvements

This work will be completed as a part of an early action item for the eventual improvements to the I-25 and Happy Canyon Road bridge and interchange. The roundabout will tie into the eventual final construction of the bridge/interchange project.

If you have questions about the project, please email HCRoundabout@castlepinesco.gov or call 303-705-0200.


  • 2023 - design and engineering services completed
  • January 2024 - contract awarded for construction services
  • Late February 2024 - construction began
  • June 21, 2024 - anticipated project completion

Traffic Impacts

May 30, 2024 Traffic Update:

We are pleased to announce the opening of limited lanes in the roundabout at Happy Canyon Road and Lagae Road beginning Monday, June 3. Access to and from the roundabout will be open from Lagae Road to the north and Happy Canyon Road to the south. The west travel lane from I-25 will also be open.

During this phase of the project, the portion of the roundabout heading east to Happy Canyon Bridge/I-25Detour map for the Happy Canyon and Lagae Road roundabout construction project. will be closed as the team completes a few final project steps, including updates to the deer guard. This closure is expected to last approximately one week and is essential to safely and efficiently complete the final construction stages. To access I-25 from Happy Canyon Road, an alternate route will be available by traveling north on Lagae Road to Castle Pines Parkway.

The temporary traffic change will allow the final construction work to be completed earlier than scheduled. The project is expected to open with complete access to the roundabout by June 21.


During the Lagae Road closure between Happy Canyon Road and Chase Lane, traffic will be detoured north to Castle Pines Parkway to access I-25. See the detour route map for details.

Detour map for the construction of the roundabout at Lagae Road and Happy Canyon Road.

*click on the image above to view the suggested detour route


The total budget for the project is $5.35 million with Douglas County contributing $1.5 million and the City contributing $3.85 million.

These project totals include realigning a portion of the existing Happy Canyon Road located within unincorporated Douglas County, constructing a roundabout on Lagae Road, constructing the east/west leg that connects directly from the proposed roundabout to the existing I-25 / Happy Canyon Road Interchange, constructing stormwater facilities, and making minor modifications to the segment of Lagae Road located immediately to the north of the roundabout.  Some of these roadway modifications are being completed as early action items for the eventual reconstruction of the Happy Canyon and I-25 interchange.

Project Visualization

Click on the image below to view a 3-D visualization of the project area, including the roundabout design. The visualization is for representative purposes only. The final product may have slight variations.

HC Roundabout

*click on the image above to view the visualization video of the project area

Roundabout Design Concept

Roundabout Design Concept Map

*Click image to enlarge

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Want to learn more about our long-term Road Solutions?

City Council has created a Plan of Action for the Streets of Castle Pines. Visit our Road Solutions page and find out how the City plans to invest heavily in our infrastructure over the next several years.

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