Have you noticed the new concrete path running alongside the Diagonal this summer and wondered why nobody's using it? You're not missing something. Near CO 52 and Mineral Road, the pavement is down, the curbs are poured, and in places it looks like it could open tomorrow.
It won't. Not for a few more months.
The nine-mile Diagonal Bikeway connecting Boulder and Longmont will not open to the public until January 2027, according to a construction update from Boulder Chamber Transportation Connections. That gap between what the path looks like and what it actually is turns out to matter for anyone in Gunbarrel who's timing a commute, a weekend ride, or a walk to Twin Lakes around this project.
Concrete Isn't the Same as Complete
The same Boulder Chamber Transportation Connections update from last December described the path as looking almost finished in several stretches, based on drone footage the group posted of the corridor. But construction on a bikeway isn't just pouring concrete. Crews are still working through the CO 52/Mineral Road intersection, where new bus rapid transit stops and bikeway underpasses are taking shape at the same time, in the same footprint. That kind of overlapping work is why a path can look done from a car window and still be off-limits.
The Colorado Department of Transportation has kept up weekly traffic-pacing bulletins for the corridor through late August 2026, which tells you the work along the Diagonal hasn't slowed down even as the visible finish line gets closer. Drivers moving through the zone should expect intermittent traffic-pacing operations, where equipment crossing the highway briefly holds traffic. CDOT's guidance is blunt on this: don't pass a pacing vehicle, and fines double inside the construction zone. If you'd rather skip the corridor altogether while this wraps up, the posted detour runs via US 287, using Ken Pratt Boulevard on the Longmont side or CO 7 on the Boulder side.
The Bus Arriving This Year Isn't the Bus Arriving Next Year
The bikeway isn't the only piece of this corridor on a staggered timeline. The CO 119 Bus Rapid Transit service, branded the Diagonal Flyer, is set to begin operating in 2026, but what "operating" means this year is narrower than what it means in 2027.
| 2026 | 2027 | |
|---|---|---|
| Bikeway | Visibly near-complete, corridor still under construction | Full 9-mile path opens to the public in January |
| Bus frequency | 30-minute service during weekday commuting hours only | Expands to daily service |
Once the Diagonal Flyer is fully built out, it will run as two routes: a Blue Line connecting Longmont to Downtown Boulder Station via 28th Street, and an Orange Line connecting Longmont to Boulder Junction at Depot Square via peak-hour service. New stations are planned in the median of CO 119 at 63rd Street, CO 52, 47th Street, and Niwot Road, which puts a stop within reach of most of Gunbarrel without requiring a transfer downtown first. But the 2026 launch is the commuting-hours version. If you're picturing hopping the Diagonal Flyer for a weekend errand this fall, that version of the service isn't here yet.
Where to Spend the Wait: Twin Lakes Open Space
While the Diagonal sorts itself out, Gunbarrel's other daily fixture hasn't changed at all, which is part of its appeal. Twin Lakes Open Space is a 42-acre wetland Boulder County purchased in January 2002, with the Left Hand Irrigation Company still holding the water rights. It sits in the middle of the neighborhood, not on the edge of it, and the rules around it are specific enough that it's worth knowing before you show up with a leash or a fishing rod.
- East Twin Lakes Trail runs 0.7 miles and is rated easy. Dogs must stay leashed here.
- West Twin Lakes Trail also runs 0.7 miles and is rated easy, but it's the off-leash side, as long as your dog stays under control.
- Fishing is allowed on both lakes, though neither is stocked.
- Swimming and wading aren't permitted.
- E-bikes are prohibited on the trail segment that follows the ditch between 63rd Street and Twin Lakes Road.
- Trailheads close at sunset, and parking isn't allowed between sunset and sunrise.
The payoff for knowing the rules is the wildlife that comes with them. Turtles and migrating birds use the wetland year-round, owls raise their young there in spring, and coyotes are audible in the evening on a fairly reliable schedule. None of that changes while the Diagonal finishes up a few blocks away, which makes Twin Lakes the easiest place in Gunbarrel to ignore the construction entirely for an hour.
The Businesses Already Sitting on the Future Route
The stretch of Gunbarrel closest to the construction is also where most of the neighborhood's dining already lives, which means the wait for the bikeway and the bus is being spent somewhere useful rather than avoided.
Avery Brewing and Proto's both sit within the same general footprint as the CO 52 work. Proto's opened as part of the Gunbarrel Center development with a full bar and Neapolitan-style pizza menu, the kind of sit-down spot that didn't exist in Gunbarrel a decade ago. Celestial Seasonings still runs guided factory tours a short distance away, one of the few tea factory tours in the country and a genuine draw for out-of-town guests. Cafe Blue, at 5280 Spine Road, keeps weekday-only hours, closed Saturday and Sunday, which makes it more of a weekday lunch habit than a weekend destination. Aperitivo, Gunbarrel's global fusion bistro built around Lavazza coffee, stays open later, Monday through Saturday from 11 a.m. to 9 p.m. and Sunday from 11 a.m. to 8 p.m.
None of these businesses are waiting on the bikeway or the bus to matter. They're already the reason people cross the Diagonal on foot or by car right now. When the path and the transit service both catch up next year, they'll just be easier to reach without a car.
What This Means for the Rest of the Year
The short version: don't test the new concrete before January, don't expect the Diagonal Flyer to replace a weekend errand run until 2027, and don't skip Twin Lakes just because the rest of the corridor is under a cone. The neighborhood's daily rhythm, the trail rules at the lakes, the weekday hours at Cafe Blue, the tea tours at Celestial Seasonings, hasn't paused for construction. It's just operating a few months ahead of the infrastructure that's supposed to make it more convenient.
If you're watching this corridor because you're weighing what it means for a home nearby, or you just want a neighborhood-level read on how the Diagonal's construction timeline is likely to play out over the next year, Wood Residential tracks these changes as part of everyday work in Gunbarrel and the surrounding Boulder County towns. Request a private neighborhood consultation if you'd like a closer look at how this stretch of the Diagonal is shaping up.
