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OCR for page 45
46 GLOSSARY Addressable chip: A computer chip added to a device to allow Inside lane: The furthest left lane of a group of adjacent lanes a computer system to identify, locate, or control that device with the same direction of travel. directly. Lane line: A pavement marking that delineates a line between Ambient light: Total illumination of an area without addi- two adjacent lanes with the same directions of travel. tional lighting sources. Laser beam: Highly amplified and coherent radiation of one Aperture angle: The angle indicating the width of a light beam. or more discrete frequencies of light focused into a straight Bidirectional: An undivided roadway with two opposing line. directions of travel. A device with two faces such that the Light-emitting diode (LED) source: Diode in which light desired effect of the device is obtained with each face (i.e., emitted at a p-n junction is proportional to the bias current; a retroreflective pavement marker). color depends on the material used. Bollard: A thick post. Luminance level: The intensity of light per unit area of its Candela (cd): Basic unit of luminous intensity. source. Centerline: The pavement marking line that bisects two Luminous intensity: Level of which light is emitted from a opposing directions of travel. source. It is a measure of the wavelength-weighted power Cone of vision: A person's field of view. A driver's lateral emitted by a light source in a particular direction. vision, typically adequate up to 20 degrees on each side. Manual activation: A method of device activation in which a Delineation: Pavement markings separating adjacent lanes of human turns on a switch. traffic. Mid-block, uncontrolled crosswalk: A crosswalk not at a road- Diode: An electronic device that restricts current flow. way intersection and without a stop sign or traffic signal at Edgeline: A pavement marking line on the right side of the the crosswalk. right lane. NEC: National Electrical Code. A standard for the safe in- Electroluminescence: Direct conversion of electrical energy stallation of electrical wiring. to light by a solid phosphor subjected to an alternating Outside lane: The furthest right lane of a group of adjacent electric field. lanes with the same direction of travel. Flashing crosswalk: Pedestrian crosswalk with in-pavement Passive detection/activation: A method of device activation markers installed to provide additional warning. in which a human does not turn on a switch, but something Guide: Something that serves to direct or indicate. Halogen lamp: A tungsten filament enclosed in a quartz else activates the device. pocket with halogen gas surrounding it. Pavement marking: Paint, retroreflective pavement markers, Illuminate: To provide or brighten with light. in-pavement markers, or other raised pavement markers Incandescent bulb: A bulb with a tungsten filament that, used on a roadway. when heated substantially, emits light. Photoelectric: Affected by a light source. In-pavement markers (IPM): An object that is placed inside Regulate: To control or direct using a set of rules typically (buried in) or on the surface of the pavement to provide enforced by a government agency. guidance to road users. Respondents: Participants who replied to the survey In-roadway lights: Defined in the MUTCD as " . . . special administered. types of highway traffic signals installed in the roadway Retroreflective pavement marker (RRPM): An object with a surface to warn road users that they are approaching a con- surface that reflects the light of a vehicle's headlight back dition on or adjacent to the roadway that might not be read- to the source, which is placed on a pavement surface. ily apparent and might require the road users to slow down Road user: A motor vehicle operator, bicycle rider, pedestrian, and/or come to a stop. This includes, but is not necessarily or person utilizing another personal mode of travel who is limited to, situations warning of marked school crosswalks, using a roadway system. marked midblock crosswalks, marked crosswalks on un- Unidirectional: An object, marking, or device that faces only controlled approaches, marked crosswalks in advance of one way. roundabout intersections . . . " Warn: To signal prudence or a danger.