The ADA and ABA standards address access for
various types of disabilities and mobility aids.
Some provisions are best understood in relation to the use of wheelchairs and powered devices.
This animation illustrates wheelchair maneuvering and requirements in the standards for clearances,
floor surfaces, and reach ranges.
Space at least 30" wide and 48" long is required to accommodate an occupied wheelchair.
To allow room for movement and sway, accessible routes must
provide a continuous clear width of at least 36".
The width can reduce to 32" minimum at points, such as doorways.
Segments with a reduced width are limited to a depth of 24",
and there must be a separation of at least 48" between them.
Where routes make a turn around an obstruction, additional space is required
depending on the tightness of the turn.
If an obstruction is at least 48" wide, additional clear width is not required.
If an obstruction is less than 48" wide, the route clear width can remain 36" minimum
if at least 60" is provided at the turn to facilitate maneuvering.
Otherwise, the clear width must be at least 42" approaching the turn,
48" minimum at the turn, and 42" beyond the turn.
Space at least 60" wide provides room for wheelchairs to pass.
Where routes are less than 60" wide, passing space 60" by 60" minimum
is required at 200' intervals.
Passing space can also be achieved at route intersections
with segments at least 48" deep.
Maneuvering clearances required at doors, which are sized according to the approach
and swing, usually require additional space beyond the minimum clear width of routes.
Room for turning is required in certain spaces, such as toilet rooms and dressing rooms.
Turning space can be provided in the form of
a 60" minimum diameter circle or a T-shaped space.
Maneuvering for turns varies by mobility aid and personal preferences and abilities.
With manual chairs, moving wheels in opposite directions is the most efficient way to turn.
Turns can also be made by keeping one wheel stationary.
Among powered devices, the turning radius can vary greatly.
Objects that provide space for knees and toes can overlap turning space.
Minimizing such overlap or avoiding it altogether is advisable to provide easier access,
especially for larger devices, such as scooters and power chairs.
Turning space can also be provided in the shape of a "T"
that is at least 60" by 60" overall with segments at least 36" wide.
This space can be oriented for approach on any segment of the T.
Objects with knee and toe space can overlap only 1 segment of the T
so that the other two remain clear for approach and backing up.
Turning within the minimum dimensions specified can be difficult using scooters and similar
devices that have a larger turning radius.
The availability of additional space beyond the minimum required will ease maneuvering.
Also, avoiding overlap of the space by an object
will better accommodate devices with front tillers.
The standards also address ground and floor surfaces.
The surfaces must be firm, stable, and slip resistant, and changes in level must be properly treated.
Abrupt level changes can be difficult to negotiate
and catch front casters unless properly edged or sloped.
Changes in level up to 1/4" are permitted without treatment.
Level changes up to 1/2" must be beveled with a slope no steeper than 1:2.
Changes in level higher than 1/2" must be ramped.
The standards also limit openings, such as grates, in ground and floor surfaces.
Surface openings that are too wide can catch wheelchair front casters,
as well as the tips of crutches and walkers.
Openings in accessible surfaces cannot exceed 1/2" in one dimension.
Openings must be oriented so that the long dimension
is perpendicular to the direction of travel.
Carpet that is thick, soft, or loose can make wheelchair maneuvering difficult.
The standards address pile height and texture and require that carpet be firmly secured.
Otherwise, rolling or buckling can occur, greatly impairing wheelchair travel.
Proper securement is needed to prevent carpet from rolling or shifting.
Wheelchair space is required at accessible building elements.
In general, this space can be oriented for a forward or side approach,
but a forward approach is required at certain elements, such as drinking fountains.
This space must be at least 30" wide and 48" long.
If space for a forward approach is recessed in an alcove or otherwise confined
on both sides more than 24", the width is increased to 36".
Clear floor space can be oriented for a side approach at most elements.
For side approaches, space that is recessed or confined on both sides more than 15"
must be at least 60" deep to facilitate maneuvering into the space.
Space for knees and toes allows people using wheelchairs to pull up sufficiently to elements
such as drinking fountains, lavatories and sinks, and dining and work surfaces.
Space for toes is 9" high and 6" deep.
The clearance must increase to 27" over a span of 3" or a rate of 6:1.
The remainder of the space to the leading edge must provide
a clearance of at least 27" for knees.
These clearances allow room for plumbing, enclosures, and supports, which cannot protrude
into the knee and toe space.
Where knee and toe space is required, it must be at least 17" deep.
The maximum total depth is 25". Space beyond this depth is not usable.
Accessible reach ranges extend from 48" to 15" above the floor or ground.
This applies to the operable parts of an element.
Forward reaches do not extend far beyond the toes.
For this reason, the reach depth over an object cannot exceed
the available knee and toe space below.
If the reach depth is greater than 20", the maximum height is reduced
from 48" to 44". The reach depth, like the knee and toe space, is limited to 25".
The side reach range is also 48" to 15" if unobstructed.
Obstructions are limited to a height of 34".
The 48" maximum height is permitted to a depth of 10".
The maximum height reduces to 46" beyond a 10" depth up to the maximum depth of 24".
The reach to objects located in corners can be difficult in view of the side reach radius.
It is advisable, though not specifically required in the standards, to avoid locating objects
in corners accessed only from a side approach.
Further guidance on the ADA and ABA standards is available from the U.S. Access Board.
This animation was developed by the U.S. Access Board in cooperation with the federal agencies
that issue the ADA and ABA standards.