South Boulder Mountain Bike Connection: Shanahan–Doudy Draw Proposal

"Drivers are often coming off the highway, and many are still going 40 or even 50 miles per hour," a rider told the Open Space Board of Trustees on Aug. 12. The rider was describing Marshall Road, which riders cross twice to reach the Marshall Mesa and Doudy Draw trail systems.

That road is the center of the debate over a bike route through the south end of Boulder's open space system. Most of the case for a Shanahan Ridge to Doudy Draw connection is about getting cyclists off Marshall Road and Eldorado Springs Drive. The city's own evaluation treats it the same way. Its draft package scores the trail route high for safety and at zero for several habitat measures, and right beside it the package lists a fix at the intersection where those two roads meet.

The route, trail by trail

Under the proposal, a continuous multi-use path would be built to the city's bike design standards by rerouting parts of trails South Boulder already uses. In order, it would:

1. Start at the Greenbriar Connector in the Shanahan Ridge neighborhood.
2. Follow Thomas Lane to the South Boulder Creek West Trail.
3. Continue south along the Mesa Trail.
4. End at the South Mesa and Doudy Draw trailheads near Eldorado Springs.

All of these trails pass through the Colorado Tallgrass Prairie State Natural Area. Boulder Reporting Lab describes the area as home to rare plants, ground-nesting birds, rare butterflies and other wildlife. Bikes are not allowed on these trails today.

Why a road keeps coming up in a trail debate

This round started in April, when mountain bikers asked for a safer bike connection in the city's multimodal survey. The Boulder Mountainbike Alliance backed the request with a direct description of the problem. "Right now, if you want to ride from Boulder to Marshall Mesa or to Doudy Draw, you're pushed onto Highway 170," the group wrote. "For adults, that's uncomfortable. For kids, it's often a non-starter."

Opponents named another way around. Some said cyclists can skip Highway 170, which is Eldorado Springs Drive, by taking the Community Ditch Trail to the south, a slightly longer ride. Cyclists answered that this route still puts them on Marshall Road. The same rider said Boulder Junior Cycling and the Fairview teams "have had multiple close calls." Eleanor Hodby told the board she viewed Marshall Road and Eldo Canyon as "rat runs for distracted drivers."

Both sides are arguing about which road cyclists should use to reach the southern trails. That shapes how the city scored the options.

How the city scored its own idea

In August 2026, the city posted a draft evaluation matrix as part of its Multimodal Assessment Project. It rates possible improvements from 0 to 4 on about a dozen and a half criteria. The Shanahan–Doudy Draw connection sits in its own section of the matrix. A note above it says "no recommendation or decision has been made regarding this connection."

The same document's south-side section has two other options for riders headed toward Marshall Mesa and Doudy Draw. One would recommend that CDOT improve the crosswalk at Marshall Road and Eldorado Springs Drive. The other would build a shade structure and restrooms at the Doudy Draw trailhead. Here is how the trail connection and the crosswalk compare on the criteria most relevant to this debate:

The two options get the same safety score for different reasons. For the trail, staff wrote that it would likely "increase safety for those biking to Doudy Draw via Marshall Mesa in that biking on a trail is inherently safer than biking on a road." For the crosswalk, staff said it would make the current access route along Marshall Road safer for cyclists. They also noted that the intersection belongs to CDOT, that redesigning it would be challenging, and that it would need a traffic study.

In other words, the city has scored a road fix that leaves the prairie alone and a prairie route that avoids the road. They tie on safety, and the trail route scores lower on every ecological measure in the table.

The prairie side of the ledger

The zeros in the trail connection's row match what opponents have said at the board's meetings. Staff wrote that adding bikes "will likely increase overall visitation, which may affect wildlife movement, access to water, and use of the area." They also flagged that a bike route could help invasive plants spread. At the Aug. 12 meeting, Bev Baker of the Boulder County Audubon Society said cyclists would harm an area that supports "multiple species of rare and declining grassland nesting birds, plants, and pollinators."

The trail connection also scored a 1 for "encounters with others," and hikers raised that concern at the board. A hiker told the board she has hiked with an elderly friend for nearly 30 years. They now hike pedestrian-only South Boulder trails because her friend can't step off the trail quickly when bikes pass. The matrix note says a trail designed for shared use could reduce some conflict, but staff still expect some bikers would see more of it.

The planning score of 1 goes back to 2011. That year, the community group running the West Trail Study Area process couldn't agree on mountain bikes, so it left the decision to staff and the Open Space Board. The board recommended keeping the ban on nearly all city trails, and in March 2011 the City Council voted to keep it. City staff say the 2011 plan allows a reroute of the South Boulder Creek West Trail, but "adding bikers would be counter to previous plan guidance." PLAN-Boulder County argues that the 2011 plan "cannot be easily changed without unraveling the interwoven agreements." The Mountainbike Alliance says considering one connection "does not mean throwing out the West TSA or reopening every decision made in 2011." The Alliance has also argued that trails could be rerouted around the most sensitive areas.

What people said before the arguments started

In June 2026, before the Aug. 12 meeting and the competing email campaigns, the city released results from its first engagement window. One question asked about improving trail connections from the Greenbriar/Shanahan area to the southern part of the system, "including bicycle connections." That wording is broader than the specific route on the table now. The city asked the question two ways, in person at trailheads and through an open online survey:

Most people in both groups supported the idea, 74% in person and 71% online. The difference is in how strongly they felt. Online responses leaned harder in both directions, with more strong support and many more strong objections, and only 12% chose neutral. That is the shape you'd expect when a debate is organized and people seek out the survey.

The city also ran a second questionnaire from Aug. 14 through Aug. 30 on this route and other proposed changes. It asked whether people would stop using the southern trails if bikes were allowed, and which factors mattered most to them. The city's project page links to the June results and the August matrix, but not to a report on the August questionnaire. The old survey link now shows a notice that the city's engagement platform is being replaced, with a new one planned for early November.

What happens Oct. 14 and after

• Wednesday, Oct. 14, 2026: The Open Space Board of Trustees meets. As of Oct. 4, the city's event page said the agenda "will be posted when available."
• October: The project timeline calls for a staff update to the board this month, followed by a refined package of solutions.
• Early November: The city's new online engagement platform is expected to launch.
• First quarter of 2027: If the board recommends it, the City Council could vote then.

The full matrix, the June results and the project timeline are all on the city's Multimodal Assessment Project page. The August meeting is covered in Boulder Reporting Lab's report, which includes the speakers quoted here. If you start hikes at the Greenbriar Connector or ride Marshall Road to reach Doudy Draw, the Oct. 14 agenda is the next document to watch.

Trail access is one of the things that makes daily life different from one South Boulder street to the next, and it is shifting this fall. If you'd like to talk through how the Shanahan Ridge and Greenbriar side fits your routines, Manzanita Fine is happy to walk through it with you. Schedule a one-on-one neighborhood consult.