All 0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Word Description
(ITS) Intelligent Transportation System
3S2 3 axle tractor with a 2 axle semi-trailer
AADT Annual Average Daily Traffic
AADTT Annual Average Daily Truck Traffic
AASHTO American Association of State Highway & Transportation Officials
Actuated Controller A traffic signal controller that receives information from vehicle and/or pedestrian detectors and provides signal timing accordingly.
Actuation The operation of any type of detector (NEMA). The word operation means an output from the detector system to the controller unit.
ADT Average Daily Traffic
ADUS Archived Data User Service
Advisory Detector The detection of vehicles on one or more intersection approaches solely for the purpose of modifying the phase sequence and/or length for other approaches to the intersection (NEMA).
Alternating Current (AC) A current which reverses direction at regular intervals. the rate of reversal is expressed in hertz (cycles per second).
Ampere The unit expressing the rate of flow of an electrical current. One ampere is the current flowing through one ohm resistance with on volt pressure.
Amplifier See Detector Amplifier.
Analog An electronic design that uses continuously varying voltages, rather than digital numbers.
ANSI American National Standards Institute.
Antenna The radiating of receiving elements utilized in transmitting of receiving electromagnetic waves (NEMA).
Apollo For information on our Apollo Classifier Click Here.
Area Detection The continuous detection of vehicles over a length of roadway wherein the call of a vehicle in the detection area is intended to be held for as long as the vehicle remains in the area of detection. (Most detectors cannot hold the call indefinitely). Frequently referred to as large-are detectors, long-loop detectors, or presence detectors.
Area Detector See Large Area Detector.
Area of Detection See Zone of Detection.
Arterial A major urban roadway usually with coordinated signals along its length.
ARTS Advanced Rural Transportation Systems
AS475 AS475 Grout
ASTM The American Society for Testing and Materials.
ATIS Advanced Traveler Information System
ATMS Advanced Traffic Management System
ATR Automatic Traffic Recorder
Auxillary Equipment Separate devices used to add supplementary features to a controller assembly (NEMA).
AVC Automatic Vehicle Classification
AWG American Wire Gauge. The standard measurement of wire size. It is based on the circular mil system. 1Mil equals .001
BMS Bridge Management System
CAAA Clean Air Act Amendments (1990)
Cable A group of separately insulated conductors wrapped together and covered with an outer jacket.
Calibrator For additional information on our Calibrator Click Here.
Calling Dectector A detector that is installed in a selected location to detect vehicles which many not otherwise be detected, and whose output may be modified by the controller unit (NEMA). This traditionally has meant a small area detector near the Stop Line, to detect vehicles the roadway from a driveway during the red or yellow signal. The detector is disconnected when the green signal is displayed so that extensions of green can only come from the appropriate Extension Detector.
Capacitance That property of a system of conductors and dielectrics which permits the storage of electricity separated charges when potential differences exist between the conductors. Its value is expressed as the ratio of an electric charge to a potential difference.
Card-Rack Mounted Detectors See Rack Mounted Detectors.
Carryover Output The ability of a detector to continue its output for a predetermined length of time following an actuation (NEMA). See Extended Call Detector.
Cascade Modem For more information on our Cascade Modem, Click Here.
CC For more information on our Centurion CC Software, or to download a current copy Click Here
Centurion CC For more information on our Centurion CC Software, or to download a current copy Click Here
Centurion Field For more information on our Centurion Field software, or to download a current copy Click Here.
Centurion Gold For more information on our Centurion Gold Software, or to download a current copy Centurion Gold
Centurion Lite For more information on our Centurion Lite Software (Windows PDA), or to download a current copy Centurion Lite
Centurion Parks For more information on our Centurion Parks Software, or to download a current copy Centurion Parks
Chain Chain
Chamfer Diagonal saw slots at the corners of square or rectangular loops to reduce the angle of bend of the loop wires at the intersecting saw slots.
Change Interval The yellow interval following the green signal indicating the change to a conflicting phase.
Channel Electronic circuitry which functions as a loop detector unit (NEMA).
Circuit A closed path followed by an electric current.
Clearance Interval A red interval that may be shown following the yellow change interval before allowing a conflicting green signal to be displayed.
CMS Congestion Management System
Coil A coiled conductor, wound on a form or core which uses electro magnetic induction to cause changes in a current.
Conductance The measure of ability to conduct electricity.
Conductor A medium for transmitting electrical current. A conductor usually consists of copper or other materials.
Conduit A tube for protecting electrical wires, wiring or cables.
Conflicting Call See Serviceable Conflicting Call.
Conflicting Phases Two or more traffic phases which will cause interfering (i.e., conflicting) traffic movements if operated concurrently.
Continuous Presence Mode Detector output continues in any vehicle (first or last remaining) remains in the field of influence (NEMA). This definition does not imply that the use of this mode guarantees that the output will continue indefinitely, as most detectors are incapable of holding a call beyond a finite interval. See Detector Mode.
Controlled Output The ability of a detector to produce a pulse that has a predetermined duration regardless of the length of time a vehicle is in the field of influence (NEMA). See Detector Mode.
Controller Assembly A complete electrical mechanism mounted in a cabinet for controlling the operation of a traffic control signal (NEMA). See also: Traffic-Actuated Controller Assembly, Semi-Traffic-Actuated Controller Assembly, Full-Traffic-Actuated Controller, and/or Pedestrian-Actuated Controller Assembly
Controller Unit A controller unit is that portion of a controller assembly that is devoted to the selection and timing of signal displays (NEMA). Also referred to as the Dispatcher or Timer.
Critical Intersection Control (CIC) An algorithm employed in traffic systems to dynamically control the split at signalized locations where the traffic patterns are such that special control, responsive to changing conditions, is needed.
Critical Lane Detection A system of hardware and software designed to provide data on traffic flow for a selected lane, usually the heaviest volume lane on an approach to a signalized intersection.
Crosstalk The adverse interaction of any channel of a detector unit with any other detector channel (NEMA). It is mutual coupling of magnetic fields that produces interaction between two or more detector units in the same cabinet when the units are operating at similar frequencies. Crosstalk results in detector outputting an actuation in the absence of a vehicle. This condition may also apply to inductive loop and devices that fail appropriate tuning, installation, configuration and/or maintenance.
CVC Continuous Vehicle Classifier
CVO Commercial Vehicle Operations
Cycle A complete sequence of all signal indications at an intersection. In an actuated controller, a complete cycle is dependent on the prescience of detector calls on all phases.
Cycle Length The time period in seconds required for a complete cycle. Cycle length is normally variable for actuated intersections unless they are a part of a coordinated system.
Decector Failures The occurrence of detector malfunctions including non-operation, chattering, or other intermittently erroneous detections.
Delayed Call Detector A detector that does not issue an output until the detection zone has been occupied for a period of time that exceeds the time preset on an adjustable timer incorporated into the detector unit.
Delayed Output The ability of a detector to delay its output for a predetermined length of time during an extended actuation (NEMA).
Delta L (L) The change in inductance.
Demand The request for service, e.g., one or more vehicles desiring to use a given segment of roadway during a specific unit of time.
Demand Control See Loop Occupancy Control
Demand Operation A mode of operation whereby the service provided at an intersection reflects the presence of deamand for that service without regard to the background cycles.
Density A measure of the concentration of vehicles, stated as the number of vehicles per mile per lane.
Density Controller Actuated controller that has timing adjustments for the selection of the allowable gap independent of the passage of time. A volume-density controller and a modified density controller are each a type of density controller.
Design Speed The speed used as typical by the designer of the detector/controller system in the kinematic analysis of the scheme under free traffic flow conditions.
Detection Zone That area of roadway within which a vehicle will be detected by a vehicle detector (NEMA). Also called "zone of detection" or "sensing zone".
Detector A device for indicating the presence of passage of vehicles or pedestrians (NEMA). This general term is usually supplemented with a modifier indicating type (e.g., loop detector, magnetic detector, etc.); operation (e.g., point detector, presence detector, etc.); or function (e.g., calling detector, extension detector, etc.).
Detector Amplifier A device that is capable of intensifying the electrical energy produce by a sensor (NEMAN). An example is a magnetic detector amplifier. A loop detector unit is commonly call an amplifier, although its electronic function actually is different.
Detector Memory The retention of an actuation of future utilization by the controller assembly. The phrase might better be detection memory to make is clearer that the memory is within the controller, not the detector.
Detector Mode A term used to describe the operation off a detector channel output when a presence detection occurs (NEMA). See Pulse Mode, Controlled Output, Continuous Presence Mode, and Limited Presence Mode.
Detector Setback Longitudinal distance between stop line and detector.
Detector System The complete sensing and indication group consisting of the detector unit in the controller, the lead-in cable, the lead-in wires, and the sensor.
Detector Unit The portion of a detector system other that the sensor and lead-in cable, consisting of an electronic assembly.
Dielectric Any insulation material that is nonconductor of electricity.
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Dilemma Zone A distance or time interval related to the onset of the yellow interval. Originally used to describe that portion of the roadway in advance of the intersection within which a driver can neither stop prior to the stop line nor clear of the intersection before conflicting traffic is released. More recently the term has been used to describe that portion of the roadway in advance of the intersection within which a driver is indecisive regarding stopping prior to the stop line or proceeding into or through the intersection. Also may be expressed as the increment of time corresponding to the dilemma zone distance.
Dilemma-Zone Protection Any method or procedure that attempts to control the end of the green interval so that no vehicle will be caught in the dilemma zone when the signal turns yellow.
Direct Current (DC) An electrical current which travels uniformly in one direction.
Drift Change in the electrical properties of the detector system or portion of it due to environmental changes particularly temperature variations and rain water.
DVDT Daily Vehicle Distance Traveled
EAL Equivalent Axle Load
Eddy Current An electric current induced within the body of a conductor when that conductor moves through a nonuniform magnetic field.
Effective Loop Area See Zone of Detection.
Encapsulation The process of filling the saw slot with sealant to surround the wires int eh slot and protect them from traffic, weather, etc.
EPA Environmental Protection Agency
EPDM EPDM Synthetic Road Tube
Epoxy A resin used in bonding.
ESAL Equivalent Single Axle
Extend Call Timing A detector with carryover output. It holds or stretches the call of a vehicle for a period of seconds that has been set on an adjustable timer incorporated into the detectors. It can be designed to begin the timing of that period when the vehicle enters the detection are, or when it leaves (NEMA). Also referred to as a "Stretch Detector".
Extended Call Detector When selected, this detector extends the output (see Carryover Output) after the vehicle departs the zone of detection for a preset time.
Extension Limit The maximum length of time that the actuations on any traffic phase may retain the right-of-way after an actuation on an opposing traffic phase. Also know as maximum green.
Failsafe As in output relay design, a type of output-relay design that produces a constant call, thereby keeping traffic moving, in the event that the detector unit fails.
Farad A unit of capacitance, usually expressed in microfarads (uF), on millionth of a farad.
Feeder Cable See Lead-In Cable.
FHWA Federal Highway Administration
Field For more information on our Centurion Field software, or to download a current copy Click Here.
Field of Influence See Zone of Detection.
Freeway Surveillance Process or method of monitoring freeway traffic performance and control system operation.
Frequency The number of times an alternating current repeats its cycle in 1 second.
Full-Traffic-Actuated Controller A type of traffic actuated controller assembly in which means are provided for traffic actuation on all approaches to the intersection (NEMA). See Also: Traffic-Actuated Controller Assembly, Semi-Traffic-Actuated Controller, and/or Pedestrian-Actuated Controller Assembly
Full-Traffic-Acuated Controller Assembly A type of traffic-actuated controller assembly in which means are provided for traffic actuation on all approaches to the intersection.
Gap The time interval between the end of one vehicle detector actuation and the beginning of the next actuation.
Gap Out Terminating of a green phase due to an excessive time interval between the actuations of vehicles arriving on the green, so green may be served to a competing phase.
Gap Reduction A feature whereby the unit extension of allowed time spacing between successive vehicles actuations on the phase displaying the green in the extensible portion of the interval is reduced (NEMA).
GIS Geographic Information System
GPS Global Positioning System
Green Extension System Hardware assembly of extended call detectors and auxiliary logic. The logic can monitor the signal display, enable or disable the selected extended call detectors, and hole the controller in artery green.
Ground The earth and all parts conductively connected to the earth.
Hand Hole See Pull Box.
Henry (h) The measure of inductance, defined as the inductance of a circuit in which a counter electromotive force of one volt is generated when the current is changing at the rate of one ampere per second.
Hertz (Hz) A term replacing cycles-per-second as an indication of frequency.
Hold On Line A connection that modifies a controller from full-actuated, isolated operation to semi-actuated, system controlled operation. It is sued as the basic tie from the local intersection to the system master.
Home Run Lead Home Run Cable. See Lead-In Cable.
Honda 100 A small motorcycle commonly considered to be the smallest registered motor vehicle. It is used as the baseline for motorized vehicle detection.
HPMS Highway Performance Monitoring System
Hz (Hertz) A measure of frequency in cycles per second.
IMSA The International Municipal Signal Association.
Inductance That property of an electric circuit or of two neighboring circuits whereby an electromotive force is generated in one circuits whereby an electromotive force is generated in one circuit by change of current in itself of in the other. The ratio of the electromotive force to the rate of change of the current. Measure in the micro Henries (uh).
Inductive Reactance The reactance (ohms) of an ideal (loos less) inductor is the product of the voltage across the inductor and the sine of the phase angle (90 degrees) between inductor voltage and current divided by the inductor current assuming sinusoidal operation.
Infrared Detector A detector that senses radiation in the infrared spectrum (NEMA). A detector installed over the roadway capable of being actuated by the passage of a vehicle through its field of emitted electromagnetic waves.
Initial Portion The first timed portion actuated controller unit including fixed, computed, maximum, minimum and added.
Interval The part of parts of the cycle during which signal indications do not change.
IRI International Roughness Index
ISTEA Intermodal Surface Transportation Efficiency Act (1991)
ITE (ITE) The Institute of Transportation Engineers.
Junction Box See Pull Box.
Junction Well See Pull Box.
Kilohertz (kHz) Thousands of hertz. A measure of frequency.
L (L) The symbol used for inductance or change in inductance.
Lead-In Cable The electrical cable which serves to connect the lead-in wire in the pull box to the input of the loop detector unit in the controller cabinet (NEMA). Sometimes called "home-run" cable or transmission line.
Lead-In Wire That portion of the loop wire that is between the physical edge of the loop and the pull box which should be twisted a specific number of times per foot. For a magnetic detector or magnetometer, it is the wire which runs fro the sensor (probe) to the pull box.
Light-Sensitive Dectector A detector consisting of a light source and photoelectric cell(s), capable of being operated by the passage of an object (e.g. vehicle, pedestrian, animal..) interrupting the beam or beams of light. When properly equipped, directional characteristics are present.
Limited Presence Mode Detector output continues for a limited period of time if vehicles remain in the field of influence. See Detector Mode.
LIP See Local Intersection Program (LIP)
Local Intersection Program (LIP) Type 170 software program developed by Caltrans which incorporated detector timing features within the program.
Locking Detection Memory A selectable feature of the circuit design for a controller phase whereby the call of a vehicle arriving on the red (yellow) is remembered or held by the controller after the vehicle leaves the detection area until it has been satisfied by the display of a green interval to that phase.
Loop Detector A detector that senses a change in inductance of its inductive loop sensor caused by the passage of presence of a vehicle near the sensor (NEMA). See also Loop Detector System.
Loop Detector System A vehicle detector that senses a decrease in inductance of its sensor loop(s) during the passage or presence of a vehicle in the zone of detection of the sensor loop(s) (NEMA). A system would also include the loop wire as well as the electronics package.
Loop Detector Unit An electronic device which is capable of energizing the senor loop(s), of monitoring the sensor loop(s) inductance, and of responding to a predetermined decrease in inductance with an output which indicates that passage or presence of vehicles in the zone of detection (NEMA). It is the electronics package, exclusive of the loop wire(s) and lead-in cable.
Loop Lead-In Wire The portion of the loop wire that is not part of the loop but is in the saw slot connecting the loop to the edge of the roadway, where it is carried in conduit to the controller or else to a pull box, where it is connected to the lead-in cable.
Loop Occupancy Control A detector/controller design using long detection loop(s) (normally 30 ft (9 m) or longer), and a controller unit operated in the non-locking mode. Loop occupancy control can utilize magnetometer detectors as well as loop detectors.
Loop System A combination of loop wire connected through lead-in cable to the detector in-put terminals.
LSI Chip An electrical component with more than 1,000 logic elements. This is "large scale integration" of miniature elements and is used in some loop detector units of digital design.
LTPP Long Term Pavement Performance
MADT Monthly Average Daily Traffic
MarMac Marmac Tape
MicroTally MicroTally
Motion Loop Dectector (Directional) An induction loop detector consisting of two separate loops either closely spaced or partially overlapping which is not affected by the passage of a vehicle except in the desired direction.
Motion Loop Detector (Nondirectional) An induction loop detector which is capable of being actuated by the passage of a vehicle over any portion of the loop.
MPO Metropolitan Planning Organization
Nails Nails are used as an anchor for road tube installation. To Purchase nails or to see our selection, Click Here.
Natural Road Tube Natural Road Tube
NEMA National Electrical Manufacturers Association (NEMA)
NHS National Highway System
Occupancy The proportion of time a detector is occupied. Occupancy is a pseudo measure of density on a roadway.
OFE Other Freeways & Expressways
OHM The unit of electrical resistance equal to the resistance though which a current of one ampere will flow when there is a potential difference of 1 volt across it.
Omega Omega Classifier
OPA Other Principal Arterial
Parks For more information on our Centurion Parks Software, or to download a current copy Centurion Parks
Pedestrian-Actuated Controller Assembly A controller assembly in which intervals, such as pedestrian WALK and clearance intervals, can be added to or included in the controller cycle by the actuation of a pedestrian detector (NEMA). Pedestrian actuation may be part of an intersection controller or be used to control a mid-block crosswalk. See Also: Traffic-Actuated Controller Assembly, Semi-Traffic-Actuated Controller, and/or Full-Traffic-Actuated Controller Assembly
Pegasus Pegasus
Phoenix II Phoenix II Product
Piezo Sensor or Disk A piezoelectric disk generates a voltage when deformed (change in shape is greatly exaggerated)
Piezo-electric Piezoelectricity is the ability of some materials (notably crystals and certain ceramics, including bone) to generate an electric field or electric potential[1] in response to applied mechanical stress. The effect is closely related to a change of polarization density within the material's volume. If the material is not short-circuited, the applied stress induces a voltage across the material. The word is derived from the Greek piezo or piezein, which means to squeeze or press. The piezoelectric effect is reversible in that materials exhibiting the direct piezoelectric effect (the production of an electric potential when stress is applied) also exhibit the reverse piezoelectric effect (the production of stress and/or strain when an electric field is applied). For example, lead zirconate titanate crystals will exhibit a maximum shape change of about 0.1% of the original dimension. The effect finds useful applications such as the production and detection of sound, generation of high voltages, electronic frequency generation, micro-balances, and ultra fine focusing of optical assemblies. It is also the basis of a number of scientific instrumental techniques with atomic resolution, the scanning probe microscopes such as STM, AFM, MTA, SNOM etc, and everyday uses such as acting as the ignition source for cigarette lighters and push-start propane barbecues.
PMS Pavement Management System
Pneumatics Pneumatics is the use of pressurized gas to effect mechanical motion. Pneumatics is that branch of technology,which deals with the study and application of use of pressurized gas to affect mechanical motion. Pneumatic power is used in industry, where factory machines are commonly plumbed for compressed air; other compressed inert gases can also be used. Pneumatics also has applications in dentistry, construction, mining, and other areas.
Presence Loop Detector An induction loop detector which is capable of detecting the presence of a standing or moving vehicle in any portion of ht effective loop area.
PSR Present Serviceability Rating
PTR Permanent Traffic Recorder (aka ATR)
RMA Return Materials Authorization.
Road Tube Road Tube Kit 1
Road Tube Kit 2
Road Tube Kit 3
Road Tube Bounce Created when a heavy vehicle travels over a section of road tube at a high rate of speed, causing it to jump, slap or hop into the air from the road grade surface. Also can occur on uneven or heavily rutted roads.
Sealant The material used in a saw slot of loop detector to seal the looped and twisted wires in the slot.
Semi-Traffic-Actuated Controller Assembly A type of traffic actuated controller assembly in which means are provided for traffic actuation on one or more but not all approaches to the intersection (NEMA). See Also: Traffic-Actuated Controller Assembly, Full-Traffic-Actuated Controller, and/or Pedestrian-Actuated Controller Assembly
Serial Cable UPP Serial Cable
Unil Serial Cable
SHRP Strategic Highway Research Program
Spike Spike
TEA21 Transportation Equity Act for the 21st Century
Titan II Titan II
TMG Traffic Monitoring Guide
Traffic Count A traffic count is a count of traffic along a particular road, either done electronically or by people counting by the side of the road. Traffic counts can be used by local councils to identify which routes are used most, and to either improve that road or provide an alternative if there is an excessive amount of traffic. Also, some geography fieldwork involves a traffic count. They are useful for comparing two or more roads, and also can be used alongside other methods to find out where the CBD of a settlement is located.
Traffic Counter A traffic counter is a device, often electronic in nature, used to count, classify and/or measure the speed of vehicular traffic passing along a given roadway. The device is usually deployed in near proximity to the roadway and uses an intrusive medium, such as pneumatic road tubes laid across the roadway, piezo-electric sensors embedded in the roadway, inductive loops cut into the roadway, or a combination of these to detect the passing vehicles. Recently, in the interest of worker safety and ease of installation, non-intrusive technologies have been developed. These devices generally use some sort of transmitted energy such as radar waves or infrared beams to detect vehicles passing over the roadway.
Traffic Tally 14 Traffic Tally 14
Traffic Tally 2 Traffic Tally 2
Traffic Tally 21 Traffic Tally 21
Traffic Tally 4 Traffic Tally 4
Traffic Tally 41 Traffic Tally 41
Traffic Tally 6w Traffic Tally 6w
Traffic Tally 77 Traffic Tally 77
Traffic Tally 8w Traffic Tally 8w
Traffic-Actuated Controller Assembly A controller assembly for supervising the operation of traffic control signals in accordance with the varying demands of traffic as registered with the controller by detectors (NEMA). See Also: Semi-Traffic-Actuated Controller Assembly, Full-Traffic-Actuated Controller, and/or Pedestrian-Actuated Controller Assembly
Trail Counter Trail Counter TTC-4420
TVT Traffic Volume Trends
TWS Truck Weight Study
uH (Micro Henry) A measure of inductance. See Inductance.
Unicorn Unicorn Classifier
Unicorn Limited Unicorn Limited Classifier
VDT Vehicle Distance Traveled
VMT Vehicle Miles Traveled
VTRIS Vehicle Travel Information System
WIM Weigh-In-Motion