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Selected Glossary of Human Factors and Safety Terms


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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 F1637-95]

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 surfaces.

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, Readability.

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 visual angle.

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 included.[ASTM F1637-95]

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.

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