Saccade. A quick eye movement
used to shift visual fixation from one point to another.
Scotopic. Related to nighttime
illumination levels in which the eye is adapted to dark and vision is
supported by the rod photoreceptors.
Slip. Loss of balance resulting
from insufficient friction between a pedestrian's foot (or foot surrogate)
and the walkway surface.
Slip resistance. The relative
force that resists the tendency of the shoe or foot to slide along the
walkway surface. Slip resistance is related to a combination of factors
including the walkway surface, the footwear bottom, and the presence
of foreign materials between them [ASTM F1637-95].
Slip-resistant. The provision
of adequate slip resistance to reduce the likelihood of a slip for pedestrians
using reasonable care on the walking surface under expected use conditions.[ASTM
Slip-resistant surface. A walkway
surface with greater slip-resistant characteristics.
Stairway. Series of steps,
or flights of steps and the landings leading from one level to another.
Step. A unit of stairway that
consists of a riser and a tread.
Stimulus-response compatibility. The
relationship between a display and its associated control. Good stimulus-response
compatibility can prevent errors. "Spatial compatibility" refers to
the spatial correspondence between displays and their associated controls;
for example, with four displays in a horizontal row, good spatial compatibility
may be achieved by placing the controls in a horizontal row directly
below their corresponding displays. "Movement compatibility" refers
to the relationship between the movement of a control and the corresponding
movement of the displayed variable; for example, good movement compatibility
may be achieved when turning a control knob clockwise, such as a volume
control of a radio, is associated with an increase in the associated
display parameter, in this case, the volume.
Tagout. Means for assuring
that machines are not turned on while being serviced. A tag is placed
on the power switch to warn operators and others not to turn on the
machine until the tag is removed by the person performing the service.
Tagout is considered less reliable than "lockout". See Lockout.
Tread. In a stairway, the horizontal
surface of a step.
Tribology. The study of the
phenomena and mechanisms of friction, wear, and lubrication of interacting
Trip. Loss of balance while walking
resulting from contact of the toe or some other portion of the foot
with an obstacle.
Visibility. The degree to which
an object (including symbols and alphanumeric characters) can be distinguished
from its background; factors affecting visibility of an object include
its size, contrast, level of illumination, and exposure time. See Legibility,
Visual angle. The angle subtended
at the eye by the linear extent of an object in the visual field. It
determines linear retinal image size.
Visual field. The area of the
external environment that is visible to the eye or eyes at a given position;
the field of vision. Visual field is usually measured in degrees of
Walkway. Walking surfaces constructed
for pedestrian usage including floors, ramps, walks, sidewalks, stair
treads, parking lots and similar paved areas which may be reasonably
foreseeable as pedestrian paths. Natural surfaces such as fields, playing
fields, paths, walks, or footpaths, or a combination thereof, are not
Warning. A means for alerting
and informing a user of a product, machine, process or environmental
condition about hazards associated with its use, adverse consequences
of improper use, and ways for avoiding adverse consequences.