Two road closures will begin this week in Boulder County as part of the Colorado Highway 119 Safety, Mobility and Bikeway Improvements Project. The closures affect 2nd Avenue in Niwot and the 83rd Street median at the intersection with CO 119/Diagonal Highway.
The Colorado Department of Transportation (CDOT) originally planned to close the Oxford Road median on September 12 for several weeks, followed by a closure of the 83rd Street median. However, due to upcoming drainage operations, CDOT has changed its schedule. The closure of the 83rd Street median will now begin on Wednesday, September 10, while the Oxford Road median closure is postponed until spring 2026.
Starting at 9 p.m. on Tuesday, September 9, CDOT will temporarily close 2nd Avenue in Niwot at northbound CO 119/Diagonal Highway to allow crews to complete median-widening work for a future Bus Rapid Transit lane. Local access on 2nd Avenue will be maintained between Murray Street and the railroad tracks just east of the highway. This closure will remain in place for all modes of transportation until the end of 2025. During this period, travelers are advised to use Niwot Road to access northbound CO 119/Diagonal Highway.
On Wednesday, September 10 at 9 p.m., CDOT will also implement a full closure of the 83rd Street median between northbound and southbound CO 119/Diagonal Highway. This closure affects all modes of transportation and is expected to last several weeks. While closed, crews will construct a raised bikeway crossing and widen the road to extend deceleration lanes.
Detour routes have been posted for alternate access. Cyclists have a designated detour route as well.
For northbound travelers on CO 119 who intend to turn left onto 83rd Street, they should continue past the intersection, turn left onto Airport Road median, then turn left again to head south on CO 119. Southbound travelers intending to turn left onto 83rd Street should continue past it, turn left onto Niwot Road median, then turn left again onto northbound CO 119; this route is also signed as a cyclist detour.
Work schedules may change depending on conditions.
By the year 2040, traffic volumes along Diagonal Highway between Boulder and Longmont are projected to increase by about one quarter compared with current levels. Higher traffic volumes can result in more congestion and delays as well as increased emissions and crash risk.
According to CDOT: “The CO 119 Safety, Mobility and Bikeway Project is constructing safety, mobility and bikeway 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 goals include improving safety throughout the corridor; maximizing movement capacity; increasing operational efficiency at intersections; improving transit times; boosting ridership; increasing overall operational efficiency; and expanding opportunities for bicycle commuting with better connectivity for cyclists and pedestrians.
