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.
This is a wonderful , analytical approach to what has become an emotional issue. There are/is plenty of terrain for all interested parties. To limit access in my opinion, is a Solution seeking a Problem.
Boulder County has an avid bike culture that contributes economically and physically to the community. To those who would limit access to bikes, I say ‘find another trail’ , there are plenty to chose from.
Thanks for the comment Thomas. My goal for the article was to be objective and not pick a side. But as an avid biker I strongly agree that limiting biking further is not a good idea.
Thank you Simin for the data. Definitely paints a picture. And combined with the % of actual reported incidents (4%) and the high percentage of pushback, this pilot is biased . We could treat trails like Boulder treats off-leash dogs: everyone who has passed the “courtesy test” gets to wear a visible tag 🤣
LOL….Love the visible tag comment. I’m sure many of the incidents revolve around situational awareness.
It should also be noted that not all trails open to cycling are actually mountain bike miles. Close to the most populated areas, Heil has the most significant elevation gain and offers a consistent intermediate level experience the entire ride and is the longest trail system of any (and is the connector) — that’s what Levy wants to choke. People who want to go for a 2-hour ride semi-close to town have limited options.
Betasso and Hall are the other after-work rides. Marshall Mesa, Coalton, and Dowdy Draw offer a long loop and that is great, but it’s primarily flat. North Sky, Joder through Heil to Hall offer a great challenging longer day. Not all trail miles are an equal experience or access and the Commissioner distorts the data to make it seem like there are more MTB trails than there are. She mentioned that we have the Kinglet Trail which is too far away for hikers and should be happy with that. It is a true shame that decisions are being made haphazardly by people who don’t even understand trail planning or how people use the trails.
Yes. Agree. I tried to address the “not all trails are equal” in the postscript. But in retrospect the postscript should have expanded further on that issue.
Thanks for adding this data-informed perspective to the discussion. I think it’s worth clarifying on an important point, though: this “alternating use” pilot is misleadingly misnamed, as it only restricts cyclists. The author states “the proposal would designate specific days or times for hikers, cyclists and equestrians,” but this isn’t entirely true. The proposal designates days when cyclists aren’t allowed, but places no restrictions on other trail users. As such, it merely restricts cyclists further, when they already aren’t able to access most trails in the Boulder area. This is bad for cyclists, bad for our outdoors community, and bad for local businesses.
Conflicts between trail users are low, as data show, and can be managed with smarter approaches like unidirectional downhill trails for short downhill segments where cyclists are likeliest to increase speed. This is the approach that modern land managers take, including in more populated areas like Jefferson County.
Thanks for the comment Nik. “the proposal would designate specific days or times for hikers, cyclists and equestrians,” was pulled directly from the county website. Based on the county’s actions at Betasso based on there earlier pilot, “periodic biking ban” is certainly a more accurate name than “alternating use.” It would be interesting to compare Jeffco with Boulder on miles of trail, user access, and trail policy approaches.
This analysis doesn’t point out that a significant portion of OSMP trail mileage is on terrain unsuitable for any but the most skilled riders owing to its steepness and actual surface. The trails around the Skyline area from Sanitas to Shadow Canyon above the Mesa trail would never be MTB accessible in most cases. The management challenges of allowing riders even downhill access would be horrendous. Uphill simply wouldn’t happen. That’s less the case for county land.
Thanks for comment Pete. I tried (but inadequately) to address this in the postscript. That is: that not all trails are equal. It is certainly a valid point that much of OSMP’s current trail inventory is unsuitable for bikes.
Thank you, Simon, for bringing actual data to a debate that has run heavy on anecdote. This is exactly the kind of analysis the county should have produced itself before proposing the pilot.
Your postscript deserves as much attention as the headline number. Miles open to bikes are not the same as miles built for bikes. BCPOS may permit cycling on 87% of its trails, but it has essentially zero miles of purpose-built bike trail on more than 100,000 acres. It’s also worth noting that if “open to cyclists” includes flat dirt paths then that should be excluded from any reasonable definition of mountain biking. When you strip out the easy flatland miles, the picture of meaningful bike access probably gets considerably darker.
Thanks for the comment Rex. I really should have expanded the postscript more. Thanks for fleshing it out more in your comments.
I appreciate the data presented but it is misleading with regards to the proposed mountain bike ban. Sure, “cycling” might be allowed on 59% of Boulder county trails, but the majority of those trails are NOT mountain bike trails. Also the proposed bike ban ONLY is being applied to trails for mountain biking. There is no proposal for limiting bike use on flat gravel trails throughout most of Boulder County. True mountain bike trails in Boulder county are very limited, and there are a lot of mountain bikers wanting to use those trails. The headline and the sub-headline are misleading. They clearly imply that mountain bikers have many trails to choose from, which is simply not true. In my opinion, the post-script does a poor job of clarifying this.
Thanks for the comment Patrick. As an avid biker I agree with your comments. I would love to see more mountain bike specific (purpose built) trails in the county. My postscript should have expanded much more on the items you mentioned. Luckily, you and others have commented and expanded on this and made the discussion richer.
This is refreshing! Thank you for putting it together. This is the type of info I wish the landmanagers included in their studies and use for decisions. The County should be gathering visitation distance decay data. How far do trail users typical travel and where are the hotspots? Within the city trails are fairly short with multiple access points. These trails see heavy foot traffic as the majority of hikers do not pass the 1 mile mark. Trails like heil are very long and create regional connections. They see less use given they are located outside of the city. The decay rate plays a bigger role on this type of trail. The majority of hikers will be seen with in the first 1/2 mile of trail with abot 50% making it to the 1 mile mark for a 2mile out and back. There are very few trail users that will make it beyond the 5 mile mark on foot. A typical 1 to 2 hour hike is about 2 to 4 miles. A typical 1 to 2 hour bike ride is 6 to 20 miles. Heil is a perfect trail for bikes as it gives the distance required for a recreational ride while providing hiking only options at the base for the same duration. The traffic is low in unlike many trails in the city. A review of heat maps supports this with bikes utilizing the full bike accessible trail network while hikers utilize short sections near the trailhead.
Thanks for your comment Travis. Agree that heat maps are very telling and a great resource.
This is extremely useful information, but doesn’t identify where the conflicts are. And are not. I would supplement this with a qualitative assessment to determine how various users value the trails and whether there are opportunities for trades based on those values. I did this for the Vail Pass Task Force and for the city of Breckenridge, Summit County, and the Forest Service and it worked out quite well. It’s harder to do in Boulder, but it’s doable.
Thanks Todd. Can you share more info on what you did for Vail Pass Task Force and the City of Breckenridge……
A fundamental problem with the COTREX data is that is apparently fails to differentiate between true singletracks and flat gravel routes. For example, the Walden Ponds trail near 75th and Jay Rd. is listed as open to bicycling, but it is hardly a mountain bike trail. It is 100% flat, wide, gravel, and not interesting or fun for mtn bikers. It’s great if you want to ride a gravel bike, or you’re a complete neophyte mtn biker, but it’s not what 95% of mtn bikers are looking for. In general, both the city and county are willing to say that gravel roads are “trails” just because they don’t allow cars and trucks. To really get at the right statistic for miles of open mtn bike trails, we are going to need an actual list of all the trails that are open, then have someone who understands this issue filter out the gravel roads/trails. I would like to know if I am wrong about COTREX. Simon Testa, can you respond?
Thanks for the comment, Gary. As with any analysis, the results are only as good as the underlying data. The COTREX dataset appeared to be the best available starting point, and I made a concerted effort to remove segments that would not generally be considered trails. The COTREX data, clipped to Boulder County, initially yielded 977 miles of mapped “trails.” Using the downloadable dataset’s attributes, I first filtered the TYPE field to remove segments classified as roads, reducing the total to 847 miles. At that point, the only remaining TYPE classification was: trail. I then filtered the SURFACE field, removing segments identified as concrete, asphalt, paved, or road surfaces. This further reduced the total to 609 miles. While no filtering method is perfect, this process was intended to focus on unpaved trail segments and exclude roads and paved pathways as much as possible using the available data. Unfortunately, I don’t currently have access to GIS mapping software. Otherwise, I would have included an interactive map showing the remaining 609 miles of trail.
This debate is about mountain biking, not the admitted miles of mostly flat paved or gravel surface trails. While the analysis is interesting, it doesn’t speak to the definition of mountain biking, which vastly different and highly restricted.
Thanks, Greg. Please see my comments above. I agree that the analysis focuses on bike access rather than mountain biking specifically. It would certainly be helpful to have more granular data. Of course, what does and does not qualify as a mountain biking trail is somewhat subjective. For example, I love riding the Dirty Bismark Loop, while many riders would probably scoff at calling it a mountain biking route. Definitions vary depending on a rider’s experience, preferences, and expectations. Given the available data, I focused on identifying trails that are accessible to bicycles and then filtered out roads and paved surfaces as much as possible.
I have an older brochure that says ” Boulder County: A Way of Life that Didn’t Happen By Accident”. True in all ways and happily our Open Space strongly values safety for an aging population, quiet uses, nature connection and exemplary soil, water and habitat protection. This is what this little paradise is all about. Limits and restraints seem impossible for Boulder bikers – but the times demand it. Instead of the endless cry baby, can’t take no for an answer persona, or worse, the selfish people of Lyons making outright outrageous illegal threats to our public land (see CO Sun) we need bikers with a land ethic. How about a new group “Bikers for Biodiversity”? Some things are more important than entertaining ourselves in the woods.
Thank you for your analysis and for all of the details The OSMP lack of access for cyclists is why our family finally started voting NO on every issue that benefits OSMP. We’ve supported them for a long time, volunteered on trails at every opportunity, and still get the message that cyclists are not wanted. It’s disappointing.
The target strategies that the “pilot” is aiming for are currently in use at Betasso. There, bike exclusion days already exist. Where in Boulder county can you find bike only days? With respect to “incompatibility,” answers are already in place within the trail systems at Heil Valley, Hall Ranch, and beyond. Heil for example is home to the Grindstone quarry trail (1.6 miles) Which connects to the lichen loop (1.25 miles). Hall is home to the nighthawk trail (4.6 miles) that connects to Button rock trail (2 miles) which in turn links more than 5 additional miles of hike only trails throughout Button rock preserve.
Boulder valley ranch is home to more than 4 miles of hike only trails that include the Degge, Shale, Hidden valley, and Mesa trails. There are further examples within the county of hike only systems. (see map zoom in to Sanitas and Chitaqua) For a full site see here. https://bouldercolorado.gov/locations/trail/search/trail