TAI
Trail Access Information
TAI
Trail Access Information
Trail Access Information (TAI)
Click below to learn more about TAI and how it should be included in all trail databases
what is TAI?
People of varying abilities need access to information prior to hiking a trail. While trail ratings such as easy, moderate, or difficult may be useful to some specific trail user groups, these labels are subjective and omit essential information about the actual conditions of a trail. What is easy to one person may be difficult or impossible to another. Trail descriptions must allow each person to determine the level of difficulty for themselves, which requires objective information about actual trail conditions.
The US Access Board and the US Forest Service have developed a solution to this problem by requiring trailhead signage to disclose objective trail characteristics—regardless of the level of access afforded by a particular trail. Such Trail Access Information (TAI) provides an objective description of each trail as the basis for informed decisions. The data enables any trail user to determine whether or not they can access a trail based on their own personal abilities. Without TAI, potential trail users are left unaware of trail conditions and their ability to hike the trail.
minimum information
In order to avoid discrimination on the basis of disability and adequately inform all potential trail users of actual trail conditions, objective trail information must be documented and disclosed to the public. At a minimum, the following Trail Access Information (TAI) should be disclosed on trailhead signage, as specified in Section 1017.10 of the Architectural Barriers Act (ABA) Accessibility Standards and Section 7.4.11.2 of the US Forest Service Trail Accessibility Guidelines:
- Length of the trail or trail segment
- Surface type and quality*
- Typical and minimum tread width
- Typical and maximum running slope (grade)
- Typical and maximum cross slope
- A statement that the posted information reflects the condition of the trail when it was constructed or assessed, including the date of the construction or assessment.
* Trail quality represents surface firmness and stability. Although absent from ABA Standards and US Forest Service trailhead signage requirements, firmness and stability is required for an accessible trail. A lack of firmness and stability is the greatest barrier to access for hikers who must use wheelchairs for mobility.
Clause 7.4.11.2 of the 2013 US Forest Service Trail Accessibility Guidelines states:
Where more extensive trail information is provided (e.g., an aerial map of the trail and related facilities), the location of specific trail features and obstacles that do not comply with the technical provisions in 7.4 should be identified and a profile of the trail grade should be included.
In addition to the requirement for TAI on trailhead signage, TAI should be included in trail apps and interactive online trail maps in order to enable spatial analysis of trail and feature data by all potential trail users.
trail attributes
The information below describes the essential trail attributes that must be documented to provide Trail Access Information (TAI).
length
Trail length helps users determine timing and difficulty when deciding on their ideal path.
running slope (grade)
Running Slope. The slope that is parallel to the direction of travel.
Architectural Barriers Act (ABA) Standards (2015), F106.5
Running Slope (Grade). The ascent or descent of a trail segment expressed as a percentage of its length, which is the difference in elevation of a section of a trail measured parallel to the predominant direction of travel. This may be expressed as a ratio of vertical distance to horizontal distance or as the percentage of change in elevation.
Forest Service Trail Accessibility Guidelines (FSTAG) (2013), Section 7.3, pg 8
The Guide to the ABA Accessibility Standards, Outdoor Developed Areas states that the running slope of a trail is measured “as a ratio of vertical distance to horizontal distance, or rise to run.” For example, a 10% slope would represent 1 foot of rise measured over 10 feet of horizontal distance, or 1 foot divided by 10 feet (0.10 or 10%).
Steeper running slopes can be more difficult to navigate due to additional effort required to climb uphill and potential increased speed caused by downhill segments. For this reason, gradual slopes are easier to navigate, while steeper slopes require shorter segments with resting intervals at the beginning and end of the slope (2015 ABA Standards 1017.8).
Clause 1017.7 of the 2015 ABA Standards specifies the following intervals for an accessible experience along steeper segments of a trail. Trail running slopes exceeding these guidelines may be more difficult or inaccessible for many trail users.
Running slope is measured at the beginning of each station. A digital level is placed on the best path of travel, parallel to the path of travel. Running slope is measured in percent, representing rise over run. This can be done using a visual clinometer or a digital level.
When measuring with a digital level, it is recommended to use a level with with feet to avoid teetering. The SmartTool™ level with SmartFeet is 24 inches in length and thus measures the grade as it would be experienced over the course of a single stride, or by a stroller or wheelchair.
technical requirements
1017.7 Slopes. The slopes of trails shall comply with 1017.7.
1017.7.1 Maximum Running Slope and Segment Length. Not more than 30 percent of the total length of a trail shall have a running slope steeper than 1:12 (8.33%). The running slope of any segment of a trail shall not be steeper than 1:8 (12%). Where the running slope of a segment of a trail is steeper than 1:20 (5%), the maximum length of the segment shall be in accordance with Table 1017.7.1, and a resting interval complying with 1017.8 shall be provided at the top and bottom of each segment.
Table 1017.7.1 Maximum Running Slope and Segment Length
| Running Slope of Trail Segment | Maximum Length of Segment | |
| Steeper than | But not Steeper than | |
| 1:20 (5%) | 1:12 (8.33%) | 200 feet (61 m) |
| 1:12 (8.33%) | 1:10 (10%) | 30 feet (9 m) |
| 1:10 (10%) | 1:8 (12%) | 10 feet (3050 mm) |
Advisory 1017.7.1 Maximum Running Slope and Segment Length. Gradual running slopes on trails are more useable by individuals with disabilities. Where the terrain results in steeper running slopes, resting intervals are required more frequently. Where running slopes are less severe, resting intervals are permitted to be further apart.
1017.8 Resting Intervals. Resting intervals shall comply with 1017.8.
1017.8.1 Length. The resting interval length shall be 60 inches (1525 mm) long minimum.
1017.8.2 Width. Where resting intervals are provided within the trail tread, resting intervals shall be at least as wide as the widest segment of the trail tread leading to the resting interval. Where resting intervals are provided adjacent to the trail tread, the resting interval clear width shall be 36 inches (915 mm) minimum.
1017.8.3 Slope. Resting intervals shall have slopes not steeper than 1:48 in any direction.
EXCEPTION: Where the surface is other than concrete, asphalt, or boards, cross slopes not steeper than 1:20 shall be permitted when necessary for drainage.
1017.8.4 Turning Space. Where resting intervals are provided adjacent to the trail tread, a turning space complying with 304.3.2 shall be provided. Vertical alignment between the trail tread, turning space, and resting interval shall be nominally planar.
7.4.3 Slope.
Trail running slopes (grades) and cross slopes shall comply with sections 7.4.3.1 and 7.4.3.2.
7.4.3.1 Running Slope (Grade). The running slope (grade) of trail segments shall comply with this section and shall be consistent over the distances cited.
- Trail running slope (grade) of up to 1:20 (5 percent) is permitted for any distance.
- The running slope of any segment of a trail shall not be steeper than 1:8 (12 percent).
- No more than 30 percent of the total trail length may exceed a running slope (grade) of 1:12 (8.33 percent).
- Where the running slope (grade) of a segment of a trail is steeper than 1:20 (5 percent), the maximum length of the segment shall be in accordance with Table 7.4.3.1, and a resting interval complying with 7.4.4 shall be provided at each end of the segment.
Table 7.4.3.1 Running Slope (Grade) and Resting Intervals
| Running Slope of Trail Segment | Maximum Length of Segment | |
| Steeper than | But not Steeper than | Between Resting Intervals |
| 1:20 (5%) | 1:12 (8.33%) | 200 feet (61 m) |
| 1:12 (8.33%) | 1:10 (10%) | 30 feet (9 m) |
| 1:10 (10%) | 1:8 (12%) | 10 feet (3050 mm) |
7.4.4 Resting Intervals.
Resting intervals shall comply with 7.4.4. Where the trail grade exceeds 1:20 (5 percent), resting intervals shall be provided as specified in Table 7.4.3.1.
7.4.4.1 Length. The resting interval length shall be 60 inches (1525 mm) long minimum.
7.4.4.2 Width. Where resting intervals are provided within the trail tread, resting intervals shall be at least as wide as the widest segment of the trail tread leading to the resting interval. Where resting intervals are provided adjacent to the trail tread, the resting interval clear width shall be 36 inches (915 mm) minimum.
7.4.4.3 Slope. The slope of a resting interval shall not exceed 1:20 (5 percent) in any direction. Where the surface is paved or is elevated above the natural ground, the slope shall not be steeper than 1:48 (2 percent) in any direction.
7.4.4.4 Turning Space. Where resting intervals are provided adjacent to the trail tread, a turning space complying with ABAAS section 304.3.2 shall be provided. Vertical alignment between the trail tread, turning space, and resting interval shall be nominally level. The trail tread, turning space, and resting interval may overlap.
cross slope
Cross Slope. The slope that is perpendicular to the direction of travel.
Architectural Barriers Act (ABA) Standards (2015), F106.5
Cross Slope. The percentage of rise to length, which is the difference in elevation, when measuring the trail tread from edge to edge perpendicular to the direction of travel This may be expressed as the percentage of change in elevation or as a ratio of vertical distance to horizontal distance.
Forest Service Trail Accessibility Guidelines (FSTAG) (2013), Section 7.3, pg 8
The Guide to the ABA Accessibility Standards, Outdoor Developed Areas states that the cross slope of a trail is measured “as a ratio of vertical distance to horizontal distance, or rise to run.” For example, a 5% slope would represent 1 inch of rise measured over 20 inches of horizontal distance, or 1 inch divided by 20 inches.
While a certain amount of cross slope is necessary for proper drainage to keep water off the trail, excessive cross slopes can increase the difficulty of traversing a trail. When the cross slope exceeds 1:48 (2.1%), wheelchair users and other hikers must exert extra effort against the force of gravity in order to maintain lateral balance. In addition, a severe cross slope can cause a wheelchair or adaptive bike user to be directed laterally in the downhill direction. Abrupt changes in cross slope greater than 5% over a distance of 24 inches can cause stumbling or falling for various trail users, especially those using wheelchairs.
According to clause 1017.7.2 of the ABA Standards, a maximum cross slope of 1:48 (2.1)% is required for trails compliant with ABA trail requirements. If drainage is necessary for a trail with a surface other than concrete, asphalt, or boards, a maximum of 1:20 (5%) cross slope is permitted. Cross slopes that exceed 1:20 (5%) will be increasingly difficult or inaccessible for many trail users.
Station cross slope is measured at the beginning of each station. A digital level is placed on the best path of travel, perpendicular to the path of travel. Cross slope must be measured in percent, representing rise over run. To identify drainage problems, a positive value can be assigned for an out-slope that drains surface water to the downhill side of the trail. Negative values indicate the trail has an in-slope to drain water towards the uphill or bank side of the trail.
When measuring with a digital level, it is recommended to use a level with with feet to avoid teetering. The SmartTool™ level with SmartFeet is 24 inches in length and thus measures the cross slope as it would be experienced over the width of a typical standing person, or by a stroller or wheelchair.
technical requirements
1017.7.2 Cross Slope. The cross slope shall be not be steeper than 1:48.
EXCEPTION: Where the surface is other than concrete, asphalt, or boards, cross slopes not steeper than 1:20 shall be permitted when necessary for drainage.
7.4.3.2 Cross Slope. The cross slope shall not exceed 1:20 (5 percent). Where the surface is paved or is elevated above the natural ground, the cross slope shall not be steeper than 1:48 (2 percent).
tread width
The tread width is the clear width of the trail, perpendicular to the path of travel. The tread width includes the usable trail surface and the area above the trail in which the trail user travels.
Forest Service Trail Accessibility Guidelines (FSTAG) (2013), Section 7.3, pg 9:
Tread Width. The visible trail surface measured perpendicular to the direction of travel.
Clear Tread Width. The width of the usable trail tread and adjacent usable surface.
Minimum Tread Width. The width of the usable part of the tread width at the narrowest point on a trail.
Minimum Trail Width. The width of the trail tread and the adjacent usable surface at the narrowest point on a trail.
The width of the trail tread determines who can access the trail. People using wheelchairs, assistive bikes, strollers, wagons, or walkers may not be able to pass through areas where the tread width reduces to less than 36 inches (or 32 inches over a distance greater than 24 inches). The average manual wheelchair has a wheelbase width of less than 28 inches. If a trail narrows to 26 inches, a person in a 28-inch wheelchair will know that they will not be able to venture past this point unless they are capable of transferring out of their chair and maneuvering their chair through this narrow location. People with visual impairment may not be able to detect objects that protrude into the trail above ground level. Before hiking a trail, each trail user should determine beforehand for themselves the minimum tread width they can safely navigate.
Clause 1017.3 of the ABA Standards specifies a minimum clear tread width of 36 inches for trails compliant with ABA trail requirements. This clearance must be maintained up to a height of 80 inches (see 1017.9 and 307). Objects may only protrude into the tread width outside the minimum 36-inch clearance. Such protruding objects generally may not protrude more than 4 inches at a height of more than 27 inches and up to 80 inches from the ground. Objects 27 inches and below may protrude any amount, but may not reduce the minimum 36 inches of tread width.
Station tread width is measured at the beginning of each station. A tape measure is placed across the full trail tread at ground level, perpendicular to the direction of the trail. Vegetation and ground obstacles, such as bushes and rocks, often define the edge of the trail tread. Border areas of the trail bed that are outside of the trail tread are not considered part of the trail tread width.
technical requirements
1017.3 Clear Tread Width. The clear tread width of trails shall be 36 inches (915 mm) minimum.
1017.4 Passing Spaces. Trails with a clear tread width less than 60 inches (1525 mm) shall provide passing spaces complying with 1017.4 at intervals of 1000 feet (300 m) maximum. Where the full length of a trail does not fully comply with 1017, a passing space shall be located at the end of the trail segment that fully complies with 1017. Passing spaces and resting intervals shall be permitted to overlap.
Advisory 1017.4 Passing Spaces. Entities should consider providing either a 60 inches (1525 mm) minimum clear tread width or passing spaces at shorter intervals if the clear tread width is less than 60 inches (1525 mm), where a trail is:
- Heavily used; or
- A boardwalk or otherwise not at the same level as the ground surface adjoining the trail.
Where the full length of the trail does not fully comply with 1017, locating a passing space at the end of the trail segment that fully complies with 1017 enables a person who uses a mobility device to turn and exit the trail.
1017.4.1 Size. The passing space shall be either:
- A space 60 inches (1525 mm) minimum by 60 inches (1525 mm) minimum; or
- The intersection of two trails providing a T-shaped space complying with 304.3.2 where the base and the arms of the T-shaped space extend 48 inches (1220 mm) minimum beyond the intersection. Vertical alignment at the intersection of the trails that form the T-shaped space shall be nominally planar.
Advisory 1017.4.1 Size. Where the passing space is the intersection of two trails, the intersection must be as flat as possible so that all of the wheels of a mobility device touch the ground when turning into and out of the passing space.
7.4.2 Clear Tread Width.
The clear tread width of the trail shall be at least 36 inches (915 mm).
EXCEPTION: Where a condition for an exception prevents achieving the required width, the clear tread width may be reduced to 32 inches (815 mm) minimum. If the condition for an exception prevents achieving the reduced width of 32 inches, comply to the extent practicable.
7.4.5 Passing Spaces.
Trails with a clear tread width less than 60 inches (1525 mm) shall provide passing spaces complying with 7.4.5 at intervals of 1000 feet (300 m) maximum. A passing space must also be provided at the end of any segment of trail that meets the requirements of 7.4, if the full length of the trail does not meet the requirements. Passing spaces and resting intervals may coincide or overlap.
7.4.5.1 Size. The passing space shall be either:
- A space 60 inches (1525 mm) minimum by 60 inches (1525 mm) minimum; or
- The intersection of two trails providing a T-shaped space complying with ABAAS section 304.3.2 where the base and the arms of the T-shaped space extend 48 inches (1220 mm) minimum beyond the intersection. Vertical alignment at the intersection of the trails that form the T shaped space shall be nominally level.
7.4.5.2 Slope. The cross slope of a passing space shall not exceed 1:20 (5 percent) in any direction.
7.4.5.3 Non-complying Segment Ends. Where a segment of the trail does not comply with 7.4, a passing space shall be located at the end of each adjacent trail segment that does comply with 7.4.
surface type & quality
The type of surface material affects certain trail requirements, such as maximum obstacle height (ABA Standards 1017.5) and maximum cross slope (ABA Standards 1017.7.2). Although the type of trail surface material may vary widely, two qualities are essential in determining the accessibility of a trail surface: firmness and stability.
According to the U.S. Access Board Guide to the ABA Accessibility Standards, Outdoor Developed Areas, “a firm trail surface resists deformation by indentations.” In Section 15.4.2 of Designing Sidewalks and Trails for Access: Part II of II: Best Practices Design Guide, the FHWA states that “Firmness is the degree to which the surface resists deformation by indentation when, in this case, a person walks or wheels across it. A firm surface would not compress significantly under the forces exerted as a person walks or wheels on it.”
In Chapter 3: Floor and Ground Surfaces of the Guide to the ADA Standards, the U.S. Access Board states that, “stable surfaces resist movement.” In the Guide to the ABA Accessibility Standards, Outdoor Developed Areas, the Access Board states that “a stable trail surface is not permanently affected by expected weather conditions and can sustain normal wear and tear from the expected uses between planned maintenances.” In Section 15.4.2 of Designing Sidewalks and Trails for Access: Part II of II: Best Practices Design Guide, the FHWA states that, “Stability is the degree to which the surface remains unchanged by contaminants or applied force, so when the contaminant or force is removed, the surface returns to its original condition. A stable surface would not be significantly altered by a person walking or maneuvering a wheelchair on it.”
Forest Service Trail Accessibility Guidelines (FSTAG) (2013), Section 7.3, pg 8–9:
Surface. The top layer of a trail.
Firm. A firm surface resists deformation by indentations. During the planning process, firmness must be evaluated for noticeable distortion or compression during the seasons for which the surface is managed, under normally occurring weather conditions.
Stable. A surface is not permanently affected by expected weather conditions and can sustain normal wear and tear from the expected use(s) of the area, between planned maintenance.
Trail surface material may range from concrete to sand, with various types being affected differently by trail use, the surrounding environment, and climate. The difficulty and accessibility of a trail are directly affected by the firmness and stability of the surfacing material on the trail. While some users may prefer trail surfaces to be slightly softer than hard, travel across a softer surface will generally be more difficult for all trail users and may exclude people with disabilities. The FHWA states the following in Section 15.4 of Designing Sidewalks and Trails for Access: Part II of II: Best Practices Design Guide:
Soft surfaces, such as dry sand or pea gravel, are more difficult for all users to negotiate and present particular hazards for those using wheeled devices including road bicycles, walkers, and wheelchairs not designed for rugged terrain….When a person walks or wheels across a surface that is not firm and stable, energy that would normally cause forward motion instead deforms or displaces the surface, so the energy is lost through slipping.
Therefore, as the firmness and stability of a trail surface worsens, the energy required to use that trail will increase, creating a more difficult and sometimes inaccessible pathway. Soft surfaces are the greatest barrier to trail access for hikers using mobility devices.
Clause 302.1 of both the 2010 ADA Standards for Accessible Design and the 2015 ABA Accessibility Standards requires the surface of an accessible route to be stable, firm, and slip resistant. The ABA Standards trail surface requirements, however, do not specify slip resistance. In Guide to the ABA Accessibility Standards, Outdoor Developed Areas, the U.S. Access Board states, “slip resistance is not required for the surface of trails because leaves, dirt, ice, snow, and other surface debris and weather conditions are part of the natural environment that would be difficult, if not impossible, to avoid.”
objective firmness and stability
Although firmness and stability are somewhat subjective terms, an objective method of recording firmness and stability levels may be used on trail surfaces. Funded by the National Institutes of Health, the Rotational Penetrometer (RP), an instrumented surface indenter (ISI), was developed by Beneficial Designs to enable mobile surface testing that provides accurate firmness and stability data of any surface type. The RP measures surface firmness by pressing an indenter into the ground surface with a specified amount of force. The distance the indenter penetrates into the surface is then recorded for a firmness reading. The stability of the surface is then measured by rotating the indenter back and forth while the force is applied and then recording the amount the indenter penetrates into the surface.
The predominant surface material and quality throughout the station should be recorded at the beginning of each station. If the material or quality changes, a new station should be recorded.
Surface characteristics should be recorded under dry or “usual” conditions. Ideally, surface should be measured in both dry and wet conditions, noting any significant difference. However, if the surface is usually wet, it should be measured according to its “usual” (i.e., wet) condition.
Surface quality is determined by firmness and stability, which is collected at the beginning of each station. Firmness and stability may be measured in multiple ways:
foot and heal test
In this method, firmness and stability is recorded in one of five categories: Paved, Hard, Firm, Soft, or Very Soft.
The person making the measurement stands on the surface with a flat foot and leans all body weight onto one foot. If the surface is indented, it is considered Soft. If the person sinks into the surface as they lean, the surface is Very Soft. If the surface does not indent, the surface is either Hard or Firm.
Next, the person again stands on the surface with all body weight on one foot. Next, the person leans all body weight on the edge of their heel and then twists the heel against the surface. Typically, if the heel leaves an indention or footprint on the surface, the surface is Firm. If there is no indentation or footprint from the heel, the surface is Hard.
Rotational Penetrometer
The Beneficial Designs Rotational Penetrometer is an instrumented surface indenter (ISI), which is an objective measurement device for measuring trail surface firmness and stability. It assesses surface firmness and stability by measuring the surface displacement resulting from a calibrated spring pressing an indenter into the surface. The indenter assembly is lowered onto the test surface and locked in place. The precision spring is released and the displacement of the indenter into the surface is measured with a precision caliper to determine surface firmness. The indenter is then twisted back and forth. The additional penetration of the indenter determines the surface stability. Typically, the Rotational Penetrometer is used to objectively measure each surface type and quality identified with the foot and heel test, rather than making the measurements at each station.
The following is not intended as a full set of instructions, but only as a brief overview. Detailed operating instructions should be obtained from the manufacturer’s user’s manual. Additional instructions beyond these overview steps are necessary to collect accurate and reliable information about a trail surface.
- Position the device on the surface to be tested.
- Stand on the surface reference plates, making sure your weight is evenly distributed on both feet.
- Gently lower the penetrator assembly onto the test surface, lock the position of the assembly, and zero the caliper reading.
- Slowly release the spring force and allow the indenter to push into the surface being tested. Record the distance the indenter has moved into the surface as the firmness reading.
- Rotate the indenter through four 90-degree rotations. Record the distance the indenter has moved into the surface as the stability reading.
Each surface type is measured in five different locations, discarding the highest and lowest combined firmness and stability readings, and the remaining readings are averaged. Typically, it will be easiest to go back and measure each surface type and quality after data obtained from the trail assessment has been analyzed to identify how much of each surface type and quality exists on the trail.
technical requirements
1017.2 Surface. The surface of trails, passing spaces, and resting intervals shall be firm and stable.
Advisory 1017.2 Surface. A firm trail surface resists deformation by indentations. A stable trail surface is not permanently affected by expected weather conditions and can sustain normal wear and tear from the expected uses between planned maintenance.
7.4.1 Surface.
The trail tread surface, including resting intervals and passing spaces, shall be both firm and stable.
obstacles
Tread obstacles (changes in level), openings, protruding objects, or any other feature not compliant with ABA or US Forest Service trail requirements could all be classified as obstacles and should be documented, as they can be a barrier or hazard to a user on the trail. While some features might not be categorized as a tread obstacle, opening, or protruding object, any feature that reduces the minimum required tread width is an obstacle.
A tread obstacle specifically refers to a vertical change in level. In Section 15.4.3.1 of Designing Sidewalks and Trails for Access: Part II of II: Best Practices Design Guide, the FHWA defines a change in level as “a difference in vertical elevation between two adjacent surfaces.” In the Guide to the ABA Accessibility Standards, Outdoor Developed Areas, the U.S. Access Board defines a tread obstacle as “anything that interrupts the evenness of the tread surface.”
Changes in level are a potential tripping hazard to all trail users. Such obstacles pose a higher risk for tripping and falling to people who have difficulty in lifting their feet, such as the elderly or children, as well as to those who use wheeled devices or assistive technology, such as canes, wheelchairs, or adaptive sports equipment. Rocks, roots, steps, or uneven transitions between adjacent surfaces can unexpectedly interrupt the evenness of the trail tread surface.
Tread obstacles may not be visibly different in height compared to the surrounding surface, but may nevertheless represent a potential hazard to trail users unaware of the difference in surface. For example, a rock located within soft dirt, though not totally visible, would interrupt the evenness of the tread surface and possibly cause tripping or injury.
Paved or hard trail surfaces, including concrete, asphalt, and boards, should be free of vertical changes in level above 0.5 inches. If the trail surface material is a substance other than concrete, asphalt, or boards, the ABA Standards permit a maximum vertical obstacle height of 2.0 inches (1017.5).
Stricter requirements for vertical changes in level on accessible routes are found in both the ADA Standards and the ABA Accessibility Standards (303), which specify a maximum vertical change in level of 0.25 inches and a maximum overall vertical height of 0.5 inches, with a maximum 1:2 (50%) beveled slope for changes in level above 0.25 inches and up to 0.5 inches. Clause R302.6.2 of the Public Right-of-Way Accessibility Guidelines also applies these requirements for shared use paths. These stricter requirements can prevent tripping of trail users who are using rollerblades, walkers and other users with limited mobility.
The Guide to the ABA Accessibility Standards, Outdoor Developed Areas defines openings as “gaps in the surface of a trail.” Openings are also a potential risk along any path. Such gaps in the trail surface can catch canes, wheels, or feet and can occur between boardwalk planks, within cracks in a rock surface, or in grates installed within the trail tread.
While it is ideal to keep openings outside the trail tread, ADA and ABA standards permit openings that do not allow the passage of a sphere more than 0.5 inches in diameter (302.3). It is also recommended (and required by the US Forest Service) to align elongated openings in trails perpendicular to the path of travel so as to avoid wheelchair casters or bicycle wheels getting caught within the openings.
The 2013 US Forest Service Trail Accessibility Guidelines defines a protruding object as
A constructed feature such as a sign that extends into the trail tread more than 4 inches (100 mm) between 27 inches (685 mm) and 80 inches (2030 mm) above the trail tread. Accessibility guidelines for protruding objects do not apply to naturally occurring objects, such as tree branches, or rock ledges. However, safety regulations or Forest Service construction and maintenance standards may define clear space and limit overhangs of natural protruding objects.
The ADA and ABA standards allow post-mounted protruding objects, such as signs, to overhang the circulation path 12 inches maximum. However, it is best practice to only apply this allowance to post-mounted objects that can only be approached from the front, as explained in Section 4.1.3 of Designing Sidewalks and Trails for Access: Part II of II: Best Practices Design Guide.
At a minimum, a tape measure should be used to document the dimensions of each feature on and above the trail tread, along with the remaining tread width. Section 7.4.11.2 of the US Forest Service Trail Accessibility Guidelines states that the location of “specific trail features and obstacles that do not comply with the technical provisions in 7.4” should be identified “[w]here more extensive trail information is provided (e.g., an aerial map of the trail and related facilities).” Non-compliant features and obstacles typically include tread obstacles (changes in level), openings, and protruding objects, though any potential barrier or hazard may be included. A GPS unit should be used to document the location of each feature.
technical requirements
1017.5 Tread Obstacles. Tread obstacles on trails, passing spaces, and resting intervals shall not exceed 1/2 inch (13 mm) in height measured vertically to the highest point.
EXCEPTION: Where the surface is other than asphalt, concrete, or boards, tread obstacles shall be permitted to not exceed 2 inches (50 mm) in height measured vertically to the highest point.
Advisory 1017.5 Tread Obstacles. The vertical alignment of joints in concrete, asphalt, or board surfaces can be tread obstacles. Natural features such as tree roots and rocks within the trail tread can also be tread obstacles. Where possible, tread obstacles that cross the full width of the trail tread should be separated by a distance of 48 inches (1220 mm) minimum.
1017.6 Openings. Openings in the surface of trails, passing spaces, and resting intervals shall not allow the passage of a sphere more than 1/2 inch (13 mm) in diameter.
Advisory 1017.6 Openings. Elongated openings should be placed so that the long dimension is perpendicular, or as close to perpendicular as possible, to the dominant direction of travel.
1017.9 Protruding Objects. Constructed elements on trails, passing spaces, and resting intervals shall comply with 307.
Advisory 1017.9 Protruding Objects. Protruding objects on trails, passing spaces, and resting intervals can be hazardous for individuals who are blind or have low vision. Signs and other post mounted objects are examples of constructed elements that can be protruding objects.
7.4.6 Tread Obstacles.
Tread obstacles on trails shall not exceed 2 inches (50 mm) in height measured vertically to the highest point. Where the trail surface is paved or is elevated above the natural ground, tread obstacles shall not exceed ½ inch (13 mm) in height measured vertically to the highest point.
7.4.7 Openings.
Openings in trail tread surfaces, trail resting spaces, and trail passing spaces shall be small enough to prevent passage of a 1/2 inch- (13 mm-) diameter sphere. Where possible, elongated openings should be placed perpendicular, or as close to perpendicular as possible, to the dominant direction of travel.
Exception. Where openings that do not permit the passage of a ½ inch (6.4 mm) sphere cannot be provided due to a condition for an exception, openings that do not permit passage of a ¾ inch (19 mm) sphere shall be permitted.
7.4.8 Protruding Objects.
Constructed features, including signs, shall not extend into the trail tread more than 4 inches (100 mm) between 27 inches (685 mm) and 80 inches (2030 mm) above the surface of the trail.
additional features
Besides these five main areas of focus, other features along the way can be recorded and/or assessed typically for size, material, and quantity. More in-depth feature assessment procedures are available through the Developed Outdoor Recreation Assessment Process (DORAP). Such features may include trailhead signs, trash cans, water spouts, benches, restrooms, and many more.
technical requirements
For information regarding technical requirements of additional features, please see chapter 10: Recreation Facilities in the Architectural Barriers Act Accessibility Standards (ABAAS) or see the US Forest Service Outdoor Recreation Accessibility Guidelines (FSORAG).
RESNA Ground and Floor Surfaces
Call for Committee Interest on Ground and Floor Surfaces