Two road closures will take place this week in Boulder County as part of ongoing work on the Colorado Highway 119 Safety, Mobility and Bikeway Improvements Project. The closures are set for 2nd Avenue in Niwot and the median at 83rd Street between northbound and southbound Highway 119/Diagonal Highway.
Initially, the Oxford Road median was scheduled to close on Friday, September 12, for several weeks, followed by a closure of the 83rd Street median. However, due to upcoming drainage operations, plans have changed. The closure of the 83rd Street median is now set for Wednesday, September 10, while the Oxford Road median closure has been postponed until spring 2026.
Starting at 9 p.m. on Tuesday, September 9, the Colorado Department of Transportation (CDOT) will temporarily close 2nd Avenue in Niwot at northbound CO 119/Diagonal Highway. This closure will allow crews to widen the median for a future Bus Rapid Transit lane. Local access will be maintained between Murray Street and the railroad tracks east of the highway. The closure will remain through the end of 2025 and affects all modes of transportation. Travelers are advised to use Niwot Road to access northbound CO 119/Diagonal Highway.
At 9 p.m. on Wednesday, September 10, CDOT will also close the median at 83rd Street between northbound and southbound CO 119/Diagonal Highway for several weeks. All forms of transportation will be affected by this closure; crossing through this intersection via the median will not be permitted during construction.
While this work is underway, crews will build a raised bikeway crossing and widen the road to extend deceleration lanes.
Detour routes have been established for motorists and cyclists:
– Northbound travelers wishing to turn left onto 83rd Street should continue past it on CO 119, turn left onto Airport Road’s median, then proceed onto southbound CO 119.
– Southbound travelers wanting to turn left onto 83rd Street should continue past it on CO 119, turn left at Niwot Road’s median, then return onto northbound CO 119—a detour that also applies to cyclists.
Work schedules may change depending on conditions.
According to projections for CO 119 corridor improvements, vehicular traffic along Diagonal Highway between Boulder and Longmont is expected to increase by about a quarter by the year 2040. This anticipated growth could lead to more congestion, delays, emissions from vehicles’ tailpipes and potentially more crashes.
The ongoing project aims to improve safety throughout the corridor while making transit travel faster and more reliable by integrating with other multimodal projects in progress along this route. Goals include increasing safety for all users—including bicyclists—maximizing how many people can move through efficiently, improving transit times and ridership numbers as well as enhancing operational efficiency across intersections throughout the area.
“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.”
