View photos and video of Diagonal construction progress

Boulder County, Colo. - Construction of the nine-mile long Diagonal Bikeway, intersection safety and bus rapid transit stations is happening! Construction is expected to be completed January 2027. The completed project will include:

• Improved safety for motorists, cyclists, and pedestrians.
• Faster and more reliable bus service between Boulder and Longmont.
• Park-n-Rides at 63rd Street and Niwot Road, and bus stops at CO 52.
• Safety improvements at many of the intersections.
• A nine-mile-long paved bikeway.

This short video starts at the Diagonal and Jay Road and shows the bikeway underpass, the sidewalk, buffered bike lane on Jay and the two newly restored left hand turn lanes from Jay to Boulder bound CO 119, a gap where the bikeway is not yet built and then towards 55th where there is another section of constructed bikeway.

The intersection of the Diagonal and CO 52/Mineral Road looks really different than it did just last year. This photo shows the road alignment, the white concrete section in the upper left part of the photo is going to be the new north bound bus rapid transit stop. The bikeway underpass is also visible in the middle of the photo.

Underpass where the bikeway leaves the median and connects to an existing path in Longmont to connect to the existing path. The Spirit of Longmont sculpture is visible in the background.

Bikeway Is Closed During Construction

Please do not enter the bikeway. It is still an active construction area and is strictly off-limits. Entering between barriers, cones or construction fencing on the bikeway or anywhere on the corridor, at any time, is dangerous for cyclists, pedestrians and construction crews and could slow down construction of the project.

Remaining project work includes:

• Constructing the bus park-in-rides at 63rd, Niwot Road and bus stations at CO 52
• Paving operations connecting the underpasses to the bikeway.
• Building two bike/pedestrian bridges.
• Installing safety railings.
• Bikeway overpass at 63rd Street.
• Installing wayfinding signage.
• Grading and seeding on the shoulders of bikeway.

Stay Informed

View the CDOT CO 119 Safety, Mobility & Bikeway page for more construction updates.

Subscribe to CO 119 Diagonal Highway Safety, Mobility and Bikeway Project Construction Updates from CDOT.

Project Contacts

• CDOT phone: 720-378-8083
• CDOT email: co119safetyandmobility@gmail.com
• Boulder County phone: 303-441-4520
• Boulder County email: aphillips@bouldercounty.gov

Boulder County wants to ensure that everyone has equal access to our programs, activities, and services. To request an Americans with Disability Act (ADA) accommodation, please email ada@bouldercounty.gov, or call 303-441-1386. If you need help in another language, please email cppfrontdesk@bouldercounty.gov or call 303-441-3930.