Landing. A level walking surface
at the top and bottom of a stairway or ramp, or between flights of stairs.
Legibility. The degree to which
an alphanumeric character can be distinguished from another; depends
on attributes such as stroke width, contrast, and illumination. See
Light adaptation. The physical
and chemical adjustments of the eye and visual system that reduces sensitivity
to light as levels of illumination are increased.
Lockout. Means for assuring
that machines are not turned on while being serviced. A lock is placed
on the power switch or control box so that operators and others may
not turn on the machine until the lock is removed by the person performing
the service. Lockout is considered more reliable than "tagout". See
Luminance. The amount of light
reflected from an object or surface. Measured in candelas per square
meter (cd/m2), or foot Lamberts (fL).
Lux (lx). A measure of illuminance,
in lumens per square meter.
lx. See Lux.
Machine guard. A rigid shield
or device that covers hazard points on a machine to prevent accidental
and injurious contact with body parts, or to control hazardous ejection
and emissions from the machine such as flying chips, air contaminants
and noise. Syn. Barrier guard.
Nosing. The forward edge of
a stair tread that extends past the riser.
OSHA. Occupational Safety and
Health Administration. Part of the U.S. Department of Labor, a federal
agency created in 1971 that has regulatory and enforcement authority
to ensure safe workplaces in the United States [OSHA Web site].
Pedestrian. A person using
legs or leg surrogates (for example, prosthetic limbs, crutches, etc.)
as the principle method of locomotion. [ASTM F1646-02].
Peripheral vision. Vision in
the region of the visual field that is supported by visual receptors
outside of the fovea.
Personal protective equipment (PPE). Safety
devices or safeguards worn by workers to protect against environmental
hazards. PPE includes helmets, safety goggles, hearing protectors, face
shields, respirators, arm guards, smocks, gloves, and safety boots.
Photometry. The measurement
of the properties of light that have an effect on vision.
Photopic. Related to daytime
illumination levels in which the eye is adapted to light and vision
is supported by the cone photoreceptors.
Photoreceptor. A specialized
nerve ending, such as a rod or cone cell in the retina of the eye, that
is sensitive to light.
PPE. See Personal Protective
Ramp. A walkway surface with
a slope greater than 1:20 (5%).
Reaction time. The time it
takes to search for a signal, detect it, interpret its meaning, decide
on a response to the signal, and implement the response to the signal.
Reaction time, which typically ranges from less than one second to over
five seconds, can be affected by a number of environmental factors,
including signal quality, signal probability, number of possible responses,
and complexity of the required response. Individual factors also may
affect reaction time. Such factors may include a person's age, familiarity
with the situation, fatigue, ingestion of medication or other drugs,
and mental workload.
Readability. The degree to
which the information content represented by groups of alphanumeric
characters--words, sentences, or continuous text--can be understood;
depends on attributes such as the spacing of characters and the spacing
between lines of characters. See Legibility.
Rise. The vertical height of
something, such as the rise of a stair or ramp.
Riser. In a stairway, the vertical
face between two treads.
Risk. A measure of the probability
and severity of injury, illness, loss, or other adverse effects.
Rod. A rod-shaped photoreceptor
in the retina of the eye that responds to low levels of illumination.
Rods are located only outside of the fovea.
Run. The horizontal extent
of something, such as the horizontal distance covered by a stairway
or ramp. In a stairway, the horizontal length of the tread, measured
from the face of one riser to the face of the next, excluding the nosing.