1 / Trails and parks
What "accessible trail" means: grade, surface, width and signs
A plain reading of the US Access Board's trail figures for grade, cross slope, surface and width, and why they describe design rules rather than any one trail.
"Accessible trail" sounds like a promise, but in federal usage it refers to a set of design rules. This page reports what the US Access Board's guide to the Architectural Barriers Act (ABA) standards says for trails, and what the Forest Service says in plainer language. The figures below are federal design standards for new or altered facilities. They are not a promise about any particular trail, and a trail built long ago or maintained differently may look quite unlike them.
Who the standards cover
The ABA of 1968 requires access to facilities designed, built, altered or leased with federal funds, and the Access Board develops the guidelines. The Board added provisions for trails, picnic and camping facilities, viewing areas and beach access routes in 2013. They apply to facilities built or altered by federal agencies, or by others on federal land under a concession contract, partnership agreement or similar arrangement. The guide says they have no legal effect on state and local governments or private entities under Department of Justice ADA rules, which may use them as guidance.
A trail, in the guide's wording, is a pedestrian route developed mainly for outdoor recreation. The trail standards apply when a trail is designed for hikers or pedestrians and connects directly to a trailhead or to another trail that substantially meets the requirements. Trails designed for other uses, such as mountain bike or equestrian trails, are not required to comply.
The figures, as the guide states them
Two terms first. Running slope, also called grade, is the lengthwise slope of a trail in the direction of travel. A running slope of 1:20 (5 percent) means one foot of rise for every 20 feet of horizontal distance. Cross slope is the side-to-side slope of the trail tread, and some of it is needed so that water drains off.
| Feature | Figure the guide states |
|---|---|
| Surface | Firm and stable; slip resistance is not required |
| Clear tread width | 36 inches minimum, kept for the entire distance of the trail |
| Passing spaces | Required where tread is narrower than 60 inches; at least 60 by 60 inches |
| Running slope (grade) | Up to 1:20 (5 percent) for any length; short steeper segments allowed, never steeper than 1:8 (12 percent) |
| Steeper segments | Up to 1:12 for 200 feet; up to 1:10 for 30 feet; up to 1:8 for 10 feet; no more than 30 percent of trail length steeper than 1:12 |
| Resting intervals | Required whenever running slope exceeds 1:20; at least 60 inches long |
| Cross slope | 1:48 (2 percent) at most on concrete, asphalt or boards; up to 1:20 (5 percent) allowed for drainage on other materials |
| Tread obstacles | One-half inch at most on concrete, asphalt or boards; 2 inches at most on other surfaces |
| Openings | Small enough that a sphere more than one-half inch across cannot pass through |
A firm surface resists indentation, and a stable one is not permanently changed by expected weather and normal wear. The guide says that does not require pavement: crushed stone, packed soil and other natural materials can qualify. It also explains that slip resistance is not required because leaves, dirt, ice and snow are part of the natural environment. A surface can therefore meet the standard and still be slick; see balance and falls outdoors for footing.
When a trail is allowed to miss the figures
The standards recognize that the outdoor setting limits what can be built. They list four conditions for exceptions: compliance is not practicable because of terrain; it cannot be done with prevailing construction practices; it would fundamentally alter the function or purpose of the facility or setting; or it is limited by laws such as the Endangered Species Act or the Wilderness Act. Where a condition applies, the guide says the trail must comply "to the extent practicable", meaning reasonably doable. When extreme or numerous conditions apply, an entire trail can be exempted.
The practical consequence is that a trail described as accessible may still have a steep or narrow stretch. This is why the signage rule is useful: a new trailhead sign on a newly built or altered trail must list the length, surface, typical and minimum tread width, typical and maximum grade, and typical and maximum cross slope, whether or not the trail meets every requirement. The guide suggests dating the information, since conditions change.
How the Forest Service puts it
The Forest Service says an accessible facility, in legal terms, is one that complies with the applicable guidelines and standards when it was built or altered. It reports more than 4,500 miles of national forest trails that comply with its Trails Accessibility Standards. Some are paved, but it says what qualifies is far broader: most have firm, stable surfaces without paving, some have short runs of steeper grade that level out for resting, and width is generally 36 inches.
Using the figures when you plan
Treat a trail description as a starting point. Compare the stated grade, surface and width with what your own device and body handle comfortably, and ask the land manager how recently the trail was assessed. The protruding-object rules cover constructed elements such as signs, not natural features like branches; see outdoors with low vision, blindness, deafness or hearing loss for planning around that. Park-level details are covered in finding accessibility information for national parks, and adaptive hiking covers pacing and turning back.
The short version
The grade, cross slope, surface and width figures come from federal design standards for new or altered trails, and exceptions are built in. They help you read a trailhead sign or trail listing, but they do not guarantee how any specific trail looks today.