CO 119 Safety, Mobility & Bikeway | Construction Phase

About the Project

By the year 2040, the Diagonal Highway between Boulder and Longmont is expected to see a 25% increase in vehicular traffic. Increased traffic can result in more congestion, delay, tailpipe emissions, and potentially more crashes. The Colorado Department of Transportation, the Regional Transportation District, and Boulder County are taking action to mitigate these outcomes and expand transportation options beyond private automobiles.

To sign up for the weekly construction update emails, follow these steps:

  • Select the "Sign up for CO 119 Mobility Project Updates" button on the right side of the page
  • Scroll to the "Construction Updates & News Releases" section, select "Subscribe to Construction Updates"
  • Enter your email address, select "Northeast Colorado" as the region, check "Front Range I-25 Corridor" and "CO 119 Safety & Mobility Improvements"
  • Submit!

The CO 119 Safety, Mobility and Bikeway Project is constructing improvements to make traveling through the corridor safer for all modes and transit travel faster and more reliable. The project is designed to integrate with other active multimodal projects on the corridor to ensure community members can safely and reliably travel throughout the corridor using their mode(s) of choice.

Project Facts

  • Program Cost: $165 million
  • Contractor: Kraemer North America
  • Timeline: Fall 2024 to Spring 2027
  • Location: Colorado Highway 119 (CO 119) between Boulder and Longmont
    • Nearest Town/City: Between Boulder and Longmont
    • Mile Point(s): 44.5 to 54.5
    • County: Boulder

Funding has been secured for implementation of the project and a Construction Manager/General Contractor (CM/GC delivery method) will be used to build the project. Construction started in September 2024.

Watch the online presentation videos below to learn more about the safety, mobility, and bikeway improvements. Email [email protected] if you wish to receive this presentation in Spanish.

General CO 119 Safety, Mobility & Bikeway Project Updates

Niwot Underpass

Project Area

CO 119 Safety & Mobility Project Map
Map showing the CO 119 Safety, Mobility, and Bikeway Project, highlighting proposed project elements between Boulder and Longmont, Colorado.

Key features include:

  • Bus Rapid Transit (BRT) Stations: Marked with red bus icons along CO 119.
  • Park-n-Ride Locations: Indicated with blue "P" icons at various stations.
  • Operational & Safety Improvements: Shown with green intersection icons.
  • Bus Queue Bypass Lanes: Denoted with a gray bus with a green arrow.

Proposed RTD BRT Routes:

  • Blue Line: Proposed with a 30-minute frequency between Boulder and Longmont, bi-directionally, weekdays and Saturdays: 6 a.m. to 9 p.m. and Sundays 7 a.m. to 7 p.m. Hourly service frequency earlier and later are also proposed to be provided.
  • Orange Line: Proposed with a 30-minute frequency between Boulder and Longmont, bi-directionally, weekdays in the peaks only (6 a.m. to 10 a.m. and 2:30 p.m. to 6 p.m.)
  • Routings of these two patterns will slightly vary within Boulder and Longmont.

Additional features:

  • Intersection reconfiguration at Mineral Road.
  • Northern and Southern Project Limits marked in Longmont and Boulder respectively.

Major roads and highways are also labeled, including Airport Road, Hover Street, Niwot Road, Mineral Road, Lookout Road, Jay Road, CO 52, CO 119, and CO 157.

Project Improvements

  • New signage, striping, and improved signal timing at all pedestrian crossings at signalized intersections.
  • Signal timing adjustments at key intersections (Jay Road, 63rd  Street, CO 52, Niwot Road, and Airport Road).
  • Physically reconfiguring the CO 52 intersection to improve safety and to accommodate new Bus Rapid Transit (BRT) stations and Boulder County’s Commuter Bikeway between the northbound and southbound travel lanes.
  • Changing access at Airport Road and CO 119 to reduce crashes and to improve safety and traffic flow.
  • A list of all stops associated with the proposed BRT service is available here.
Map showing the planned CO 119/Diagonal Bikeway, highlighting underpass and overpass additions and bike and pedestrian path connections between Boulder and Longmont, Colorado
Map showing the planned CO 119/Diagonal Bikeway, highlighting underpass and overpass additions and bike and pedestrian path connections between Boulder and Longmont, Colorado.

Project Goals

  • Improve safety in the whole corridor
  • Maximize the number of people able to move through the corridor
  • Maximize intersection operational efficiency
  • Improve transit travel times and increase ridership
  • Maximize corridor-wide operational efficiency
  • Increase opportunities for bicycle commuting and connectivity to the bicycle and pedestrian network.

Project Benefits

  • Vehicles can move through the corridor faster, with shorter wait times at traffic lights, resulting in less fender benders and crashes
  • Traveling the corridor by bus will take about half the time it currently does
  • More frequent bus service supports greater travel flexibility
  • Safer and more comfortable experience accessing the corridor on foot
  • Integration between Bus Rapid Transit, Park-n-Rides, pedestrian crossings, and Boulder County’s Commuter Bikeway enables commuters to switch travel modes safely and reliably

Project Schedule

  • Construction began in September of 2024
  • The project is scheduled for completion in Spring of 2027

Traffic Impacts for the Week of May 18 to 24

Construction Impacts

  • Monday, June 2, to Friday, June 6, 7 a.m. to 5 p.m., there will be various right shoulder closures on southbound Colorado Highway 119/Diagonal Highway, between Jay Road and Hover Street, for traffic signal work.
  • Monday, June 2, 9 a.m. to 5 p.m., there will be various, intermittent single lane closures on southbound and northbound CO 119/Diagonal Highway, corridor-wide.
  • Monday, June 2 to Tuesday, June 3, 10 a.m. to 2 p.m., there will be a single, left lane closure on southbound CO 119/Diagonal Highway between Airport Road and Hover Street for detour set-up.
  • Wednesday, June 4 to Friday, June 6, 6 p.m. to 6 a.m., there will be various, overnight single lane closures on southbound CO 119/Diagonal Highway between Airport Road and Hover Street to shift traffic and set traffic barriers.

Airport Road Lane Closures Rescheduled

The lane closures on Airport Road at CO 119/Diagonal Highway has been postponed. New dates will be posted when available.

Motorist Detour

Southbound travelers on Airport Road will need to detour to southbound CO 119 and cross the median at Niwot Road to return to northbound CO 119.

Business Center Way Closure

The closure of Business Center Way at southbound CO 119/Diagonal Highway has been rescheduled to begin Monday, June 9 and will last through this fall. Business Center Way at southbound CO 119/Diagonal Highway, between South Fordham and Hover streets, will be closed to all modes of transportation.

In addition, southbound CO 119 traffic will be shifted in this area, and the southbound CO 119 bike lane between the Dry Creek Drive bike path and South Fordham Street will be closed. These closures are necessary for the bikeway underpass construction. Please follow the signed detour routes below.

Motorist Detour

Use South Fordham Street to Dry Creek Drive to access businesses near Business Center Way.

Cyclist Detour

Follow the sidewalk to Dry Creek Drive, continue on Dry Creek Drive to turn onto South Fordham Street, and continue to southbound CO 119. Business Center Way will be closed to cyclists during this time.

Traffic-pacing Operations

Intermittent traffic-pacing operations will occur on CO 119/Diagonal Highway throughout construction while crews move equipment across the highway. Traffic will move slower and may result in brief traffic holds as part of this work. Please be patient and do not pass the traffic-pacing vehicles — passing them poses a safety risk to all drivers on the road. Thank you for your patience!

Respect the Cone Zone

As you travel through the construction zone, please stay in designated traffic areas. The construction site is strictly off-limits for drivers, cyclists and pedestrians. Entering between barriers or cones at any time is extremely unsafe for travelers and project crews. Law enforcement is on site regularly to monitor traffic, and fines are doubled in the construction zone.

Help Ease Traffic: Explore Alternative Transportation During Construction

Hey, drivers! We know construction along CO 119/Diagonal Highway can be a hassle, and we're working hard to improve this corridor for everyone. In the meantime, we encourage the use of alternate modes of transportation to help reduce traffic and make your commute easier. Whether it’s carpooling, biking or using public transit, every little bit helps ease congestion and keep things moving smoothly for everyone.Thanks for your patience and support – we’ll get there faster together!