This commentary is by Simon Testa, a retired geologist, self-described data nerd and regular BRL contributor who lives in Boulder. He is an avid Flatiron scrambler and the author of “Best Flatiron Scrambles.”
Boulder County is widely recognized for its abundance of outdoor recreation opportunities. The City of Boulder frequently ranks among the nation’s premier outdoor communities due to its easy access to world-class rock climbing, hiking, trail running and cycling.
Despite this reputation, the county is often criticized for providing limited mountain bike access.
That criticism has recently intensified as Boulder County considers a pilot program that would test alternating trail use on select trails. Rather than allowing all user groups on a trail at the same time, the proposal would designate specific days or times for hikers, cyclists and equestrians. County officials say the program is intended to improve safety and enhance the trail experience. Opponents, many within the mountain biking community, argue that it would unfairly penalize bikers by further limiting access to trails when they already have less access than hikers.
The concept is not entirely new. Boulder County already uses an alternative-use schedule at Betasso Preserve, where biking is prohibited on Wednesdays and Saturdays following a 2013 study of alternative-day trail use.
The proposal has generated significant public discussion. Boulder Reporting Lab has reported on ongoing developments and published two opinion pieces presenting opposing perspectives on the pilot, each attracting substantial reader engagement.
- Rex Madden: Boulder County’s trail-use pilot unfairly targets mountain bikers
- Suzanne Bhatt: Why Boulder County should test alternating trail-use days
To help inform this discussion, I set out to answer several basic questions: How many miles of trails are there in Boulder County? Which agencies manage them? And what proportion of those trails are open to different user groups?
For this analysis, I used data from the Colorado Trail Explorer (COTREX), a statewide trail database developed by Colorado Parks and Wildlife. COTREX catalogs more than 45,000 miles of trails and serves as a navigation and information resource for hikers, cyclists, equestrians and other outdoor users. The platform compiles trail data directly from more than 200 local, state and federal land managers, making it one of the most comprehensive trail datasets available in Colorado.
I clipped the statewide dataset to the Boulder County boundary, removed roads and paved trails included in the database, and recalculated trail lengths to account for routes that cross county lines. The resulting dataset provides a countywide inventory of official trails and their permitted uses.
The analysis identified 609 miles of trails within Boulder County. The largest land managers are the U.S. Forest Service, City of Boulder Open Space and Mountain Parks (OSMP) and Boulder County Parks and Open Space (BCPOS), which together manage approximately 75% of all trail mileage in the county.
Hiking is permitted on all 609 miles of trails. Equestrian use is allowed on 457 miles (75%), while cycling is permitted on 357 miles (59%), though access varies significantly by land manager.
The data indicate that cyclists can use the smallest share of trails in Boulder County. Among the county’s major land managers, Boulder County Parks and Open Space is the most bike-accessible, allowing cycling on 105 of its 121 trail miles (87%). By comparison, the U.S. Forest Service allows cycling on 98 of 179 miles (55%), while OSMP permits cycling on just 57 of its 159 miles (36%). Rocky Mountain National Park does not allow bicycles on any of its 38 miles of trails within Boulder County.
Those differences likely reflect each agency’s distinct mission, legal obligations and recreation priorities.
The distribution of bike access is particularly striking. Although OSMP manages 26% of all trail mileage in Boulder County, it accounts for only 16% of the county’s bike-accessible trail miles. Boulder County Parks and Open Space, meanwhile, manages just 20% of total trail mileage but provides nearly 30% of all bike-accessible miles. These differences help explain why perceptions of trail access can vary dramatically depending on where recreationists spend their time.
Trail access in Boulder County is often discussed in broad terms, but the data reveal a more nuanced picture. While 59% of trail miles are open to cycling, access varies dramatically among land managers. As county officials debate changes to trail management, these numbers provide important context for understanding both the realities of access and the differing perspectives of trail users.
Postscript: This analysis treats all trail miles equally and does not evaluate whether individual trails are appropriate for different users. Nor does it assess trail quality or the user experience they provide; some trails may be well suited for biking but less appealing for hiking, and vice versa. Additionally, the percentage of different trail user groups is not considered. My goal is not to advocate for any particular outcome, but rather to provide a quantitative overview of Boulder County’s trail network and its permitted uses.
