Glossary Terms Flashcards
a device that communicates information about pedestrian timing in non-visual format such as audible tones, verbal messages, and/or vibrating surfaces
Accessible Pedestrian Signal
the flashing-light signals, with or without warning gates, together with the necessary control equipment used to inform road users of the approach or presence of trains at highway-rail grade crossings or highway-light rail transit grade crossings
Active Grade Crossing Warning System
a sensor that transmits energy, a portion of which is reflected or scattered from a vehicle or other objects and surfaces in its detection zone, back toward the receiving aperture of the sensor
Active Sensor
a traffic signal controller that receives information from vehicle and/or pedestrian sensors and provides appropriate signal timing
Actuated Controller
a type of traffic control signal operation in which some or all signal phases are operated on the basis of actuation
Actuated Operation
initiation of a change in or extension of a traffic signal phase through the operation of any type of detector
Actuation
a standardized effort intended to provide an architecture hardware and software platform that can support a wide variety of Intelligent Transportation Systems (ITS) applications including traffic management, safety, security and others
Advanced Transportation Controller (ATC)
a current that reverses its magnitude and direction of flow at regular intervals. The rate is expressed in hertz (cycles per second)
Alternating Current (ac)
a standardized wire gauge system used since 1857 for the diameters of round, solid, nonferrous, electrically conducting wire
American Wire Gauge (AWG)
requirements ensuring equal opportunity for persons with disabilities in employment, State and local government services, public accommodations, commercial facilities, and transportation
Americans with Disabilities Act of 1990 (ADA)
the unit expressing the rate of flow of electrons through a conductor. One of these is the current flowing through a 1-ohm resistance with 1-volt pressure
Ampere
an electronic design that uses continuously varying voltages, rather than discrete digital values
Analog
all lanes of traffic moving towards an intersection of a midblock location from one direction, including any adjacent parking lane(s)
Approach
a main street generally considered to be a thoroughfare with preferential right-of-way
Arterial
separate devices used to add supplementary features to a controller assembly
Auxiliary Equipment
a day representing traffic volumes normally and repeatedly found at a location; typically a weekday when volumes are influenced by employment or a weekend day when volumes are influenced by entertainment or recreation
Average Day
a board within the controller cabinet upon which are mounted field terminals, fuse receptacles or circuit breakers, and other portions of the controller assembly not included in the controller unit or auxiliary devices
Back Panel
cycle length run at the master controller that, once at the start of the cycle, outputs the system reference to the local controllers. May also be run at a controller operating TBC, which supervises the actuated operation of the intersection
Background Cycle
through or green elapsed time between the first and last possible vehicle permitted through an intersection on a progressive coordination system
Band (Green Band)
a highway traffic signal with one or more signal sections that operates in a flashing mode
Beacon
a group of separately insulated conductors wrapped together and covered with an outer jacket
Cable
manages more than 45,000 miles of California’s highway and freeway lanes, provides inter-city rail services, permits more than 400 public-use airports and special-use hospital heliports, and works with local agencies
California Department of Transportation (Caltrans)
a registration of a demand for right-of-way by traffic at a controller unit. It comes to the controller from a traffic flow sensor that is outputting an actuation
Call
since 1927, the Canadian Standards Association’s (CSA) Canadian Electrical Code has provided the signature standards for addressing shock and fire hazards of electrical products in Canada which is regularly updated to address changing technology and operating conditions
Canadian Electrical Code, CE Code (CEC), or CSA C22.1 code
also known as variable message sign (VMS) and dynamic message sign (DMS). These are traffic control devices used for the traffic warning, regulation, routing and management, and are designed to affect the behavior of motorists (thus improve the flow of traffic) by providing real-time highway related information
Changeable Message Sign
a closed path followed by an electric current
circuit
a coiled conductor, wound on a form or core, which uses electromagnetic induction to cause changes in a current
Coil
a medium for transmitting electrical current. It consists of copper or other electrically conductive materials
Conductor
a device used to detect and respond to improper or conflicting signal indications and improper operating voltages in a traffic controller assembly. Monitors ‘faults’ in controller operation (such as conflicting phases), monitors condition of controller (voltage and programming)
Conflict Monitor Unit (CMU)
two or more traffic phases which will cause interfering (conflicting) traffic movements if operated concurrently
Conflicting Phases
a complete electrical device in a cabinet for controlling the operation of a highway traffic signal
Controller Assembly
that part of a controller assembly that is devoted to the selection and timing of the display of signal indications. Also referred to as the Dispatcher or Timer. Another controller class standardizes hardware modules and uses specialized software to implement traffic management functions
Controller Unit
the adverse interaction of any channel of a sensor or sensor electronics unit with any other channel in that or another device. This can occur via mutual coupling of magnetic fields in nearby inductive loops
Crosstalk
any portion of a roadway at an intersection or elsewhere distinctly indicated as a pedestrian crossing by lines on the surface, which may be supplemented by a contrasting pavement texture, style or color
Crosswalk
the time required for one complete sequence of signal indications
Cycle Length
the lack of all signal indications at a signalized location. It is most commonly associated with power failures, ramp meters, beacons, and some moveable bridge signals
Dark Mode
the request for service. Example: one or more vehicles desiring to use a given segment of roadway during a specified unit of time
Demand
a mode of operation whereby the service provided at an intersection reflects the presence of demand for that service without regard to background cycles
Demand Operation
a measure of the concentration of vehicles, stated as the number of vehicles per mile per lane
Density
established in 1966 as a federal Cabinet department of the US government concerned with transportation. Its mission is to serve the US by ensuring a fast, safe, efficient, accessible and convenient transportation system that meets our vital national interests and enhances the quality of life of the American people, today and into the future
Department of Transportation (DOT)
that area of the roadway within which a vehicle will be detected by a vehicle sensor. Also called the zone of detection, sensing zone, area of detection, detection area, effective loop area, field of influence, field of view, or footprint
Detection Zone
a device used for determining the presence or passage of vehicles or pedestrians
Detector
an electronic device that energizes the wire loop(s), monitors the loop(s) inductance by filtering and amplifying the signals it receives, and responds to a predetermined decrease in inductance with an output that indicates the passage or presence of vehicles in the detection zone
Detector Amplifier (or Electronics Unit)
an electric current that is time-independent or, by extension, periodic current the direct component of which is of primary importance
Direct Current
a type of signal section designed to include both a yellow arrow and a green arrow
Dual-Arrow Signal Section
a special traffic control signal that assigns the right-of-way to an authorized emergency vehicle
Emergency Vehicle Traffic Control Signal
prohibits specific types of job discrimination in certain workplaces
Equal Employment Opportunity (EEO)
a device used to turn highway traffic signal indications on and off at a repetitive rate of approximately once per second
Flasher
a mode of operation in which at least one traffic signal indication in each vehicular signal face of a highway traffic signal is turned on and off repetitively
Flashing Mode
is a radar system where a known stable frequency continuous wave energy is modulated by a triangular modulation signal so that it varies gradually and then mixes with the signal reflected from a target object (vehicle) with this transmit signal to produce detection
Frequency-Modulated Continuous Wave (FMCW)
a type of traffic control signal operation in which all signal phases function on the basis of actuation
Fully-Actuated Operation
a type of conduit used in traffic signals installations (typically in drilling installations), made of a dense, economical, hydrocarbon-plastic having good moisture barrier and chemical resistance but low gas barrier properties
High-Density Polyethylene (HDPE) or Polyethylene High-Density (PEHD)
a power operated traffic control device by which traffic is warned or directed to take some specific action. These devices do not include signals at toll plazas, power operated signs, illuminated pavement markers, warning lights, or steady-burn electric lamps
Highway Traffic Signal
an international educational and scientific association of transportation professionals who are responsible for meeting mobility and safety needs. It facilitates the application of technology and scientific principles to research, planning, functional design, implementation, operation, policy development and management for any mode of transportation
Institute of Transportation Engineers (ITE)
improves transportation safety and mobility and enhances productivity through the use of advanced information and communications technologies. It encompasses a broad range of wireless and wire line communications-based information and electronics technologies
Intelligent Transportation Systems (ITS)
dedicated to providing quality certification programs for the safe installation, operation and maintenance of public safety systems; delivering value for members by providing the latest information and education in the industry
International Municipal Signal Association (IMSA)
a) the area embraced within the prolongation or connection of the lateral curb lines, or if none, the lateral boundary lines of the roadways of two highways that join one another at, or approximately at, right angles, or the area within which vehicles traveling on different highways that join at any other angle might come into conflict; b) the junction of an alley or driveway with a roadway or highway shall not constitute an intersection
Intersection
a beacon used only at an intersection to control two or more directions of travel
Intersection Control Beacon
the part if a signal cycle during which signal indications do not change
Interval
the order of appearance of signal indications during successive intervals of a signal cycle
Interval Sequence
a signal face displaying signal indications to permit or prohibit the use of specific lanes of a roadway, or to indicate the impending prohibition of such use
Lane-Use Control Signal
a solid state device embodying a PN junction, emitting optical radiation when excited by an electric current. It is a PN junction semiconductor device that, by spontaneous emission, emits incoherent optical radiation by injecting electrons and/or holes across the PN junction
Light-Emitting Diode (LED)
a selectable feature of the circuit design for a controller phase, whereby the call of a vehicle arriving on the red (or 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
Locking Detection Memory
an active sensor composed, in part, of one or more loops of wire whose inductance decreases in response to the passage or presence of a vehicle in the detection zone of the loops
Loop Detector
a passive device that senses changes in the Earth’s magnetic field caused by the movement of a ferrous-metal vehicle in or near its detection zone. It is placed under or in the roadway to detect the passage of a vehicle over the sensor. These sensors generally detect only moving vehicles. Also known as induction and search coil magnetometers
Magnetic Detector
the street normally carrying the higher volume of vehicular traffic
Major Street
device used to continually check for the presence of conflicting signal indications and other malfunctions and to provide an output response to conflict or malfunction. It is an advanced type of conflict monitor that also communicates and monitors controller function
Malfunction Management Unit (MMU)
defines the standards used by road managers nationwide to install and maintain traffic control devices on all streets and highways. It is published by the Federal Highway Administration (FHWA) under 23 Code of Federal Regulations (CFR), Part 655, Subpart F
Manual on Uniform Traffic Control Devices (MUTCD)
defines the standards used by road managers nationwide to install and maintain traffic control devised on all streets and highways in Canada
Manual on Uniform Traffic Control Devices for Canada (MUTCDC)
a control device for supervising and monitoring a system of secondary (local) controllers, maintaining definite time interrelationships and/or accomplishing other supervisory functions. In the case of traffic responsive operation, it generally includes computation equipment and recording equipment
Master
a packaged circuit or device easily removed without tools and contains a specified function. Frequently is duplicated to handle similar functions in different areas such as phase modules, load switch modules, etc
Module
a device used by power companies to measure very high resistance to earth ground
Megger (MegOhm Meter)
one million ohms, which is the unit of electrical resistance
Megohm
the street normally carrying the lower volume of vehicular traffic
Minor Street
is a standard that governs the use of electrical wire, cable, and fixtures and electrical and optical communications cable installed in buildings. It was developed by the NEC Committee of the American National Standards Institute (ANSI) was sponsored by the National Fire Protection Association (NFPA), and is identified by the description ANSI/NFPA 70-XXXX, the last four digits representing the year of the NEC revision
National Electrical Code (NEC) or NFPA 70
is a trade association of choices for the electrical manufacturing industry. Founded in 1926 and headquartered near Washington D.C., its approximately 450 member companies manufacture products used in the generation, transmission and distribution, control and end-use of electricity. These products are used in utility, medical imaging, industrial, commercial, institutional and resicential applications
National Electrical Manufacturers Association (NEMA)
a mode of actuated controller unit operation that does not require memory. In this mode of operation, the call of a vehicle arriving on the red (or yellow) is forgotten or dropped by the controller as soon as the vehicle leaves the detection area
Non-Locking Memory
the percentage of time a sensor’s detection zone is occupied. It is a pseudo-measure of density on a roadway
Occupancy
the time difference, or interval in seconds or percentage of cycle length, between the start of the green indication of the coordinated phase and the system reference signal
Offset
the ability of a vehicle sensor to detect the passage of a vehicle moving through the detection zone and to ignore the presence of a vehicle stopped within the detection zone
Passage Detection
an interval during which the flashing UPRAISED HAND (symbolizing DONT WALK) signal indication is displayed. When a verbal message is provided at an accessible pedestrian signal, the verbal message is ‘wait’
Pedestrian Change Interval
the time provided for a pedestrian crossing in a crosswalk, after leaving the curb or shoulder, to travel to the far side of the traveled way or to a median
Pedestrian Clearance Time
a signal head, which contains the symbols WALKING PERSON (symbolizing WALK) and UPRAISED HAND (symbolizing DONT WALK) that is installed to direct pedestrian traffic at a traffic control signal
Pedestrian Signal Head
a mode of traffic control signal operation in which, when a CIRCULAR GREEN signal indication is displayed, left or right turns are permitted to be made after yielding to pedestrians and/or oncoming traffic
Permissive Mode
it has two different meanings in traffic signal terminology: 1) NEMA - a vehicular (blank) is a (blank) that is allocated to one specific vehicular traffic movement (eastbound through traffic as timed by a dual ring controller unit). 2) Traditional - a part of the cycle allocated to any specific traffic movement receiving the right-of-way or to any combination of traffic movements receiving the right-of-way simultaneously during one or more intervals
Phase
predetermined order in which the phases of a cycle occur
Phase Sequence
a group of vehicles or pedestrians traveling together as a group, either voluntarily or involuntarily, because of traffic signal controls, geometrics, or other factors
Platoon
a type of conduit used in traffic signal installation, it is a thermoplastic material. Thermoplastic materials are those that can be melted again and again. (Blank) is commonly used in the construction, industrial, and healthcare sector
Polyvinyl Chloride (PVC)
the transfer of normal operation of a traffic control signal to a special control mode of operation
Preemption Control
the ability of a vehicle sensor to detect a moving or stopped vehicle in its detection zone
Presence Detection
an inductive loop detector that is capable of detecting the presence of a standing or moving vehicle in any portion of the effective loop area (ITE)
Presence Loop Detector
a type of traffic control signal operation in which none of the signal phases function on the basis of actuation
Pretimed Operation
a means by which the assignment of right-of-way is obtained or modified
Priority Control
a mode of traffic control signal operation in which left or right turns are permitted to be made when a left or right GREEN ARROW signal indication is displayed
Protected Mode
a button to activate predestrian timing
Pushbutton
a repeating sound that informs approaching pedestrians that they are required to push a button to actuate pedestrian timing and that enables pedestrians who have visual disabilities to locate the pushbutton
Pushbutton Locator Tone
number of vehicles stopped or slowly moving in a line, where the movement of each vehicle is constrained by that of the lead vehicle
Queue Length
a highway traffic signal installed to control the flow of traffic onto a freeway at an entrance ramp or at a freeway-to-freeway ramp connection
Ramp Control Signal
see Ramp Control Signal
Ramp Meter
an operational mode for an actuated controller whereby a phase, either vehicle or pedestrian, is displayed each cycle whether demand exists for it or not. It is placed into operation usually in a temporary or emergency situation
Recall
an optional interval that follows a yellow change interval and precedes the next conflicting green interval
Red Clearance Interval
the permitting of vehicles and or pedestrians to proceed in a lawful manner in preference to other vehicles or pedestrians by the display of signal indications
Right-of-Way (Assignment)
two or more sequentially timed and individually selected conflicting phases so arranged as to occur in an established order
Ring
a geographical arrangement of intersecting roadways
Roadway Network
a type of traffic control signal operation in which at least one, but not all, signal phases function on the basis of actuation
Semi-actuated Operation
a signal face, for controlling a left turn movement that sometimes displays a different color of circular signal indication than the adjacent through signal faces display
Separate Left-Turn Signal Face
a signal face, for controlling both a left turn movement and the adjacent through movement that always displays the same color of circular signal indication that the adjacent through signal face or faces display
Shared Left-Turn Signal Face
a thin strip of material that extends outward from and parallel to a signal face on all sides of a signal housing to provide a background for improved visibility of the signal indications
Signal Backplate
the establishment of timed relationships between adjacent traffic control signals
Signal Coordination
that part of a traffic control signal provided for controlling one or more traffic movements on a single approach
Signal Face
an assembly of one or more signal sections
Signal Head
that part of a signal section that protects the light source and other required components
Signal Housing
the illumination of a signal lens or equivalent device
Signal Indicaiton
that part of the signal section that redirects the light coming directly from the light source and its reflector, if any
Signal Lens
a device that can be mounted inside a signal visor to restrict visibility of a signal indication from the side or to limit visibility of the signal indication to a certain lane or lanes, or to a certain distance from the stop line
Signal Louver
the right-of-way, yellow change, and red clearance intervals in a cycle that are assigned to an independent traffic movement or combination of movements
Signal Phase
the assembly of a signal housing, signal lens, and light source with necessary components to be used for providing one signal indication
Signal Section
two or more traffic control signals operating in signal coordination
Signal System
the amount of time allocated for the display of a signal indication
Signal Timing
the part of a signal section that directs the signal indication specifically to approaching traffic and reduces the effect of direct external light entering the signal lens
Signal Visor
a threshold condition that, if found to be satisfied as part of an engineering study, shall result in analysis of other traffic conditions or factors to determine whether a traffic control signal or other equipment is justified
Signal Warrant
a beacon used to supplement a SPEED LIMIT sign
Speed Limit Sign Beacon
a division of the cycle length allocated to each of the various phases (normally expressed in percent)
Split
serving an intersection one approach at a time
Split Phasing
the continuous illumination of a signal indication for the duration of an interval, signal phase, or consecutive phases
Steady (Steady Mode)
a beacon used to supplement a STOP sign, a DO NOT ENTER sign, or a WRONG WAY sign
Stop Beacon
any fitting used for making a convenient electrical connection
Terminal
control systems in which basic coordination is provided by a highly accurate real time clock within the traffic signal controller. This information is used to determine the local signal timing of offset and cycle/split or actuated timing based on the Time-of-Day/Day-of-Week. Also called time-based coordinated control
Time-Based Coordination
timing plans which are pre-developed based upon traffic counts taken on the roadways. Signal timing usually has a minimum of three different timing plans, those being the A.M. (morning) peak period, P.M. (evening) peak period, and off-peak period
Time-of-Day (TOD)
any highway traffic signal by which traffic is alternately directed to stop and permitted to proceed
Traffic Control Signal (Traffic Signal)
is a national association with a mission to promote the provision of safe, secure, efficient, effective, and environmentally and financially sustainable transportation services in support of Canada’s social and economic goals
Transportation Assciation of Canada (TAC)
This publication contains specifications for transportation electrical equipment with focus on Intelligent Transportation Systems (ITS). Included are specifications for the following type of equipment: general, enhanced controller unit and associated modules, auxiliary and ITS cabinet units, detector sensor units, elements and isolator models, ITS cabinet assembly, and peripheral and controller
Transportation Electrical Equipment Specifications (TEES)
two insulated conductors twisted together with each end marked for identification
Twisted Pair
controller design feature that adjusts the duration of initial interval for the number of vehicles in the queue
Variable Initial Interval
a device that communicates, by touch, information about pedestrian timing using a vibrating surface
Vibrotactile Pedestrian Device
a type of signal face or signal section designed (or shielded, hooded, or louvered) to restrict the visibility of a signal indication from the side, to a certain lane or lanes, or to a certain distance from the stop line
Visibility-Limited Signal Face or Signal Section
a measurement of how many volts of alternating current are being carried, Alternating current is current which constantly changes in amplitude, and which reverses direction at regualr intervals
Volts of Alternating Current (VAC - for 120 VAC)
an interval during which the WALKING PERSON (symbolizing WALK) signal indication is displayed. When a verbal message is provided at an accessible pedestrian signal, the verbal message is ‘walk sign’
Walk Interval
a beacon used only to supplement an appropriate warning or regulatory sign or marking
Warning Beacon
the first interval following the green interval during which the yellow signal indication is displayed
Yellow Change Interval
