Accident. An unintentional event resulting in fatality, injury, illness, or property damage.

ANSI. American National Standards Institute. A private, non-profit organization that administers and coordinates voluntary industry standards in the United States. ANSI standards have been developed for equipment such as safety goggles, helmets, power tools, elevating work platforms, and roadway lighting equipment.

Anthropometry. The technology of measuring human physical traits such as size, reach, mobility, and strength.

ASTM. American Society for Testing and Materials. A private, non-profit organization that provides an international forum for the development and publication of voluntary consensus standards for materials, products, systems, and services. ASTM standards include those for test methods for determining slip-resistance, design and construction guidelines for safe walking surfaces, design and installation of grab bars, and design and manufacture of amusement park rides.

Attention. Direction and concentration of cognitive resources. “Divided attention” occurs in situations in which two or more separate tasks or mental operations must be attended simultaneously, for example, looking for road signs and scanning traffic while steering a vehicle. “Focused attention” occurs in situations in which one information source must be attended to the exclusion of others, for example trying to find a particular road sign in a group of road signs. “Selective attention” occurs in situations in which one source of information is inappropriately monitored to the exclusion of other relevant information sources, such as being so engrossed in talking on a cell phone that a driver misses his freeway exit.

Balance. A state of bodily equilibrium.

Barrier guard In machine guarding terminology, 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. Machine guard.

Biomechanics. A discipline that studies various aspects of physical movements of the body and body members.

Boom. A long pivoting structure or arm that extends from an upright to lift or carry something, such as on a crane or backhoe.

Brightness. The subjective attribute of light intensity in which brightness implies higher light intensities and dimness implies lower light intensities.

CAL-OSHA. California Division of Occupational Safety and Health. (See OSHA).

Candela. Abbr. cd. A unit of luminous intensity equal to 1/60 of the luminous intensity per square centimeter of a blackbody radiating at the solidification temperature of platinum. Also called “candle” or “standard candle” or “new candle”.

cd. Candela.

Coefficient of friction. The ratio of the friction force between two objects and the force pressing the objects together. “Static coefficient of friction” is the ratio of the hoizontal force needed to initiate a slipping action of an object along a surface, and the vertical force on the surface. “Dynamic coefficient of friction” is the ratio of the horizontal force needed to continue a slipping action of an object along a surface, and the vertical force on the surface. A higher coefficient indicates greater surface traction.

Cone. In eye physiology, a cone-shaped photoreceptor in the retina of the eye responsible for fine visual acuity and color vision. Cones function only at daylight levels of illumination.

Contaminant. An undesirable liquid or solid material on a walkway surface. Contaminants pose slip and trip hazards.

Contrast. The difference in luminance between two areas.

Contrast ratio. A mathematical expression describing the difference in luminance between two areas; the contrast ratio can be expressed as L1/L2 or as (L2L1)/L2, where L1 is the luminance of the first area and L2 is the luminance of the second area.

Control. In human-machine interaction, a mechanism for regulating or guiding the operation of a tool, apparatus, machine or other system; examples include push button, switch, knob, wheel, lever, and pedal.

Dark adaptation. The physical and chemical adjustments of the eye and visual system that make vision possible in low levels of illumination by increasing its sensitivity to light.

dB. Decibel.

Decibel. A measure of sound intensity.

Display. Any method of presenting information, such as a highway sign, warning buzzer or TV monitor.

Ergonomics. See “Human Factors.”

Fall. An unintended drop to a walkway or other surface resulting from a loss of balance.

fc. See foot candle.

fL. See foot Lambert.

Foot candle (fc). A measurement of illuminance, in lumens per square foot.

Foot Lambert (fL). A measurement of luminance.

Footwear. Anything worn on a foot that is intended to contact the ground while walking, such as shoes, boots, sandals and slippers.

Fovea. A small depression in the center of the retina that has the highest density of cones and the greatest visual acuity. The fovea has a diameter of about one to two degrees of visual angle.

Friction. A force acting at the interface between two objects that resists the motion or tendency to motion of one object relative to the other. (See also Coefficient of friction.)

Glare. Brightness in the field of view that exceeds the luminance to which the observer has adapted, and may result in annoyance, discomfort, or degraded visibility.

Handrail. A bar, pipe, or rail that is typically grasped with a hand and used for support and guidance along stairways, ramps, and walkways.

Hazard. Potential for an activity, condition, or circumstance to cause injury, illness, or other damage to people, property, or the environment.

Hertz (Hz). A measurement of frequency, in cycles per second, in which one cycle per second equals one Hertz. Applied to cycling phenomena such as the vibration of sound waves or the refreshing of a video image.

Human factors. A multidisciplinary science that studies human biological, physical, psychological, and social characteristics and applies information about those capabilities and limitations to the design, operation, and evaluation of tools, tasks, procedures, and environments for safe, effective, and productive human use. Syn. Ergonomics.

HFES. Human Factors and Ergonomics Society. A non-profit, multidisciplinary organization of professionals involved in the field of human factors. The Society promotes study and dissemination of knowledge about human characteristics that are applicable to safe, efficient, effective and productive human interaction with tools, machines, processes and environments.

Hz. See Hertz.

IIPP. See Injury and Illness Prevention Program.

Illuminance. The amount of light falling on a surface. Measured in units of lux (lumens per square meter) or foot candles (fc, lumens per square foot).

Incidence rate. Rate of job-related injuries and illnesses.

Incident. A distinct event, often one that disrupts the normal operation or procedure.

Injury and Illness Prevention Program (IIPP). Cal-OSHA-required safety program that must be established, implemented, and maintained by every California employer. Program elements address responsibility, compliance, communication, hazard assessment, accident/exposure investigations, hazard correction, training and instruction, and record-keeping.

Interlock. Mechanism, such as a switch, that turns off power to a machine whenever a safety device, such as a guard, is disabled.

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 Readability.

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 Tagout.

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. See 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.

Pedestrian. A person using legs or leg surrogates (for example, prosthetic limbs, crutches, etc.) as the principle method of locomotion. [per 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 Equipment.

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.

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. [per 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.