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Suggested Citation:"Glossary." National Academies of Sciences, Engineering, and Medicine. 2008. Applications of Illuminated, Active, In-Pavement Marker Systems. Washington, DC: The National Academies Press. doi: 10.17226/14182.
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Page 45

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

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TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 380: Applications of Illuminated, Active, In-Pavement Marker Systems (IPMs) explores the state of IPM technology, experiences with IPM applications, and potential IPM research needs.

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