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Diagonal Highway improvements move forward

Boulder County Planning Commission approves plans for safety, bus rapid transit and bikeway along Colo. 119
Conceptual rendering of Colo. 119 Bikeway, Source: Boulder County

Construction for improvements on Colo. 119, also known as Diagonal Highway, could begin as soon as spring next year.

On Wednesday, the Boulder County Planning Commission unanimously recommended that the Boulder County Board of Commissioners conditionally approve the mobility and bikeway projects on the highway connecting Longmont and Boulder.

The Colorado Department of Transportation, Regional Transportation District and Boulder County are joint applicants for the project that aims to build safety and mobility improvements along with a bikeway from Boulder to Longmont.

The three agencies are working together and plan to have one contractor take on the $160 million project, which will be completed in phases over several years. The project has secured about $132 million in funding so far and continues to seek other sources.

Colo. 119 is the highest crash corridor for motorists in Boulder County and the second highest for bicyclists, which is what has made it a priority for the county and state agencies. Additionally, bus transit in the area can be slow and unreliable, while it’s estimated that traffic along the corridor will increase by 25% by 2040.

The Diagonal improvements are considered the “spine” of the project aiming to improve the connection between Boulder and Longmont, with the cities looking at other improvements within their limits to improve the corridor.

Several changes are proposed along the highway, one of the most significant being at the intersection between Colo. 119 and Colo. 52, also known as Mineral Road, which will be split like other intersections along the corridor.

Airport Road and Colo. 119 will also be reconfigured due to the high number of broadside crashes seen at that intersection. The median road between southbound and northbound Colo. 119 will become one way toward Airport Road.

There will also be general intersection improvements at Jay Road, 63rd Street, Niwot Road and Airport Road along with Park and Ride upgrades at 63rd Street and Niwot Road.

Bus Rapid Transit is a priority along the corridor with queue bypass lanes for buses to be added at Jay Road, 63rd Street, Colo. 52, Niwot Road and southbound Airport Road. Bus Rapid Transit stations are planned at 63rd, Colo. 52 and Niwot Road.

The bikeway side of the project would include at least six underpasses currently being designed, but is pending funding. Members of the public requested additional underpasses at Niwot Road and Airport Road, which are under consideration. The proposed bikeway would connect into both Boulder and Longmont’s existing multi use path systems.

The planning commission was enthusiastic about the project, though they noted a number of safety concerns that they urged the county commissioners to consider as well. There were several other wishes for the project that the commission hoped could be addressed one day.

“We can't, I don't think, initially do everything we could possibly want on this project,” Vice-Chair Gavin McMillan said. “If we can, I’ll leave it to you all to try and figure that out. It's an expensive project. It’s a big project. I hope there will be pieces in the future that add on to this.”

The details of the plan are about 30% complete, and Boulder County staff will review the plan again when it reaches 90% completion. With approval from the Boulder County commissioners, the hope is to begin working on this project in a phased approach as soon as next year.