ITS Definitions

There are a huge range of acronyms and specialist terms used in Intelligent Transport Systems:


141's Traffic Signal Controller Configuration Specification Forms (now MCH1827)


AADT Average Annual Daily Traffic

ACC Adaptive Cruise Control

ACSF Automatically Commanded Steering Function (as part of UN Reg. 79 on Steering Equipment)

AEB Autonomous Emergency Braking

all red Traffic signal period when all signals display red aspect

ANPR Automatic Number Plate Recognition

arm Highway radiating from a junction

ARM Availability Reliability Maintainability

arrow Traffic signal aspect with a symbol indicating a direction

arterial reversion Traffic signal reversion to a nominated stage in the absence of demands

aspect Traffic signal display for a single colour or symbol (I.E. Red aspect)

ATM Active Traffic Management

audible signal A device producing a sound to indicate right of way to pedestrians

availability A measure of the percentage of time that a system is operational without failure

AVL Automatic Vehicle Location


backing board A board mounted around a signal head to increase contrast and improve visibility

bCall Breakdown Call

blackout Traffic signal period in a pedestrian sequence when neither the Red or Green figure symbols are illuminated

bleep and sweep An audible signal variant used to minimise confusion at closely located adjacent crossings

box sign An internally illuminated regulatory sign mounted alongside a traffic signal head

BRT Bus Rapid Transit

bus priority A facility to reduce delay to buses at traffic signals


cabinet On street equipment housing

cabling Wiring between discreet pieces of equipment (Power, Communications)

call Traffic signal demand for a phase or stage

call/cancel A preconfigured time delay before a demand is placed and which can also cancel the demand after a further time delay

capacity The maximum flow that can proceed through a certain point in a given period of time

carriageway That part of a road or highway constructed for the use of vehicular traffic

CAT Contractor Assessment Toolkit

CAV Connected and Autonomous Vehicle

CCTV Closed Circuit Television

CDM The Construction (Design and Management) Regulations

CDMF Common Data Management Facility

central reserve The median strip seperating the two halves of a dual carriageway

CIS Customer Information System

C-ITS Cooperative Intelligent Transport Systems

classified count A count where flows for different classes of vehicle are recorded separately

CLF Traffic signal mode of operation - Cableless Linking Facility - locally stored plans brought in by time-of-day selection

CLS Central light source

COBA Cost Benefit Analysis software tool

configuration Hardware/software equipment customisation for a specific site or functional requirement

conflict Traffic signal feature where individual movements cannot safely operate at the same time

congestion Where traffic volume exceeds capacity

connected vehicle Communications capability to increase situational awareness and reduce or eliminate crashes (V2V and V2I)

controller Equipment which operates facilities such as traffic signals

coordination A facility which relates the operation of a signalised junction with that of neighbouring junctions

count An enumeration of vehicles at a point over a specific time period

cycle One complete sequence of the operation of traffic signals

cycle time The duration of a traffic signal cycle


demand A call inserted when a detector is activated when its associated phase is displaying the Red aspect

demand dependent Traffic signal feature where a phase or stage are only active if demanded

detector Equipment used to register the presence of vehicles or pedestrians

DfT Department for Transport

dimming Reduction in the brightness of signal displays at nightime to reduce glare to roadusers

DMRB Design Manual for Roads and Bridges

DSRC Dedicated Short-Range Communication

duct Sub-surface pipes used to carry cabling

DVR Digital Video Recording

DVSA Driver and Vehicle Standards Agency (formerly VOSA)


early cut-off A traffic signal feature where a particular traffic movement is stopped whilst other movements operate concurrently

early start A traffic signal feature where a particular traffic movement starts before other movements in the same stage

eCall Emergency Call

ECU Electronic Control Unit

effective green time A period of time which takes account of vehicle lag when starting and stopping

EMC Electromagnetic Compatibility

ETM Electronic Ticket Machine

extension A call inserted when a detector is activated when its associated phase is displaying the Green aspect


fall back Traffic signal feature which changes the mode of operation when a higher priority mode is curtailed

FAT Factory Acceptance Test

FEP APP Front End Processor Application

FMS Fault Management System

filter arrow A green arrow which appears when an associated traffic movement is not active, and is extinguished when the associated traffic movement green aspect is displayed

fixed time Traffic signal mode of operation - uses predefined maximum green times


gantry Structure over carriageway used to mount equipment on

gating The use of traffic signals to restrict the flow of traffic at a point with the aim of improving the efficiency of traffic flow at a downstream point

GIS Geographic Information System

GLONASS Russian Satellite Navigation System (similar to GPS)

GPRS General Packet Radio Service (mobile data)

GPS Global Positioning System

green wave A control strategy for a linear system of traffic signals which attempts to synchronise the start of green at a junction with the arrival of a platoon from the preceding junction

GSM Global System for Mobile communications


HA Highways Agency (now Highways England, but HA still used in Acronyms)

HALOGEN Highways Agency Logging Environment

HAPMS Highways Agency Pavement Management System

HATRIS Highways Agency Traffic Information Services

HE Highways England (formerly HA)

headway The gap between two successive vehicles

high speed road A road where the 85th percentile speeds are 35mph (56km/h) or above

HOV High-Occupancy Vehicle

HUDAS Historical UTMC Data Analysis System


IMS Incident Management System

indicative green arrow A green arrow which indicates that vehicles may proceed in the direction shown whilst an associated full green signal is displayed. Usually associated with a early cut-off of oppossing traffic

inter-green Safety period between a phase green terminating and another phase green starting

interstage period Period between one stage terminating and another stage starting

invitation period The period whilst a steady green figure is displayed at a signalised crossing facility

ISO International Organization for Standardization

isolated control Where the operation of a signalised junction works independantly to surrounding junctions

INM Integrated Network Management

ITS Intelligent Transport Systems

ITS-G5 European standard for vehicular communication on IEEE 802.11p


junction Point where two or more roads intersect


lamp Light source used in signals

lamp monitoring Traffic signal safety feature which automatically senses lamp failures

lane control signals Overhead signals comprising a downward pointing green arrow and a red cross to indicate the permitted operation of a traffic lane

LCD Liquid Crystal Display

LED Light emitting diode - solid state alternative to traditional lamps

lens Translucent face of a signal display

LEPP Local Environmental Practice Plan

link Term used to describe connections between junctions in a highway network.

LINSIG Computerised traffic modelling tool for the assessment of traffic signal designs

LKA Lane Keeping Assistant

loop Wire cut into the carriageway surface used with an inductive loop detector to register the presence of a vehicle

loop feeder Cable connecting a loop with its associated inductive detector unit

loop tails Wire ends which connect between the loop and the side of the carriageway

lost time Portion of traffic signal cycle where no traffic flows

LRT Light Rapid (Rail) Transit

LTN Local Transport Note


manual mode Traffic signal mode of operation - controlled from manual (police) panel

mast arm A pole with a cantilevered outreach for mounting equipment

maximum green The maximum green period which a phase can be extended for in VA mode when a conflicting phase in a different stage has been demanded

maximum green The minimum green period which a phase can be active for in any mode

MIDAS Motorway Incident Detection and Automatic Signalling

MIS Management Information System

mode The method of control which a traffic signal controller is operating in, such as Manual, Vehicle Actuated etc

MOVA Traffic signal mode of operation - Microprocessor Optimised Vehicle Actuation

movement A specific traffic route through a junction


NFDB National Faults Database

node In a transport network, typically a junction or part of a junction

NRTS National Road Telecommunications Services

NTCC National Traffic Control Centre


OAD Offline Analysis Database

occupancy Period that a vehicle is determined to be present by a vehicle detector

OCR Optical Character Recognition

offset The difference in time between a specific point in the cycle at a junction and a reference point

opposed right turn A right turning movement which is in conflict with oncoming traffic

opposed phases Phases which are not permitted to run together by the controller but which do not control conflicting traffic movements

opposed traffic Traffic proceeding in opposite directions

optical unit Equipment components which incorporate Lens, Reflector, Light Source and Housing to form a signal display

OSCADY Computerised traffic modelling tool for the assessment of traffic signal designs

OTP Open Telematics Platform

overlap Phases which are active in successive stages

over saturation Situation where traffic volume exceeds capacity


parallel stage streams Two or more complete sequences of stages within the same controller which operate at the same time enabling two junctions or parts of a junction to be controlled with or without interaction between them

pcu The basic unit of traffic flow equal to the equivalent of a typical car (passenger car unit)

Pelican crossing A pedestrian crossing using far-side pedestrian indicators with a flashing amber/flashing green man period where vehicles are permitted to move subject to giving way to pedestrians (PEdestrian LIght CONtrolled crossing)

phantom A false impression that an aspect is illuminated caused by incident light being internally reflected back through the lens

phase Traffic signal displays which operate for a particular approach and which operate simultaneously

phase diagram A diagram which illustrates the phase activity in all stages of a traffic signal controller cycle

platoon A group of vehicles moving together where the behaviour of each vehicle is influenced by the vehicle in front

platoon dispersion The tendency for platoons to breakup under free running conditions

PMR Private Mobile Radio

POPE Post Opening Project Evaluation

portable signal A traffic signal designed to be used for temporary installations at road works

presence The period when a vehicle or person is present within a zone of detection

pre-signal A traffic signal installed in advance of a highway feature such as a junction, to meter traffic flow to the downstream location

primary signal A traffic signal located on the near-side adjacent to the Stop-line

PROM A solid state memory component - Programmable Read Only Memory

protected movement A signalled movement (commonly a right turn) where conflicting movements are held against a red signal

PTZ Pan/Tilt/Zoom

Puffin crossing A pedestrian crossing that uses near-side pedestrian signal heads and an extendable All-Red crossing period which is instigated by a push button request accompanied by a pedestrian detector demand (from Pedestrian User Friendly INtelligent crossing).

push button A switch pressed by pedestrians to register a demand

push button box A pole mounting housing for a push button


queue A stationary or slow-moving file of traffic where the progress of a vehicle is determined by that of the preceding vehicle


RCC Regional Control Centre

RCD Residual Current Device

RCP Remote Control Parking

red lamp monitoring Safety feature of traffic signal installation to verify the operation of the Red aspects

regulatory sign A sign indicating a traffic regulation (such as a prohibited movement)

remote monitoring A system to report equipment failures automatically

reserve capacity The proportion of spare capacity on a particular link or lane

RFID Radio Frequency Identification

RIU Regional Intelligence Unit

R&CPGS Route & Car Park Guidance System

Road Safety Audit A formal procedure for the independent evaluation of highway schemes to identify safety hazards

root The plinth installed in the ground to which a cabinet is mounted on top of

RRRAP Road Restraint Risk Assessment Process

RTPI Real Time Passenger Information

R-TIS Real Time Information Screens


SAT Site Acceptance Test

saturation flow The maximum flow (usually expressed in pcu or vehicles per hour) obtained at a stop line during green from a discharging queue

SCOOT Traffic signal mode of operation - Split, Cycle, Offset Optimisation Technique, uses real time traffic data to minimise stops and delays for UTC controlled areas

SDE Speed Discrimination Equipment

secondary signal A traffic signal located beyond the Stop-line which duplicates the display of the primary signal

shuttle working A system where signals are used to control a single lane operating in alternating directions

signal A dynamic indication presented to road users

signal display The combination of illuminated aspects in a signal head which provides a control instruction to traffic

signal head The enclosure for a signal display, typically mounted on a traffic signal pole

signal pole A pole used to mount equipment, such as signal heads and push buttons

signal sequence The sequence of signal displays

solar cell A light sensitive device mounted on signals to initiate dimming of the lamps during darkness

split The division of available green time within a signal cycle between stages

stage The period within a traffic signalling cycle that gives right of way to one or more particular traffic movements. A stage starts when the last of its associated phases commences and ends when the first of its associated phases terminates

start up sequence The controlled order through sequence which signals progress from the off/standby mode to normal operation

stop line A transverse marking across the carriageway adjacent to the primary signal to indicate where vehicles should stop

stud A square or circular metallic or thermoplastic marker installed on a road surface to indicate the line of a pedestrian crossing

SVD A Selective Vehicle Detector which responds only to certain vehicles identified by their characteristics or by an electronic tag


tactile indicator An indicator (typically a rotating tactile cone) which indicates the presence of the green figure signal for the benefit of visually impaired pedestrians at signalised crossings

tactile paving Paving which provides visually impaired pedestrians an indication of the location of road crossings, provide route guidance and warn of potentially hazardous locations, such as platform edges

TCS Traffic Control System

temporary signals A traffic signal using the same type of signal equipment as permanent signals but which is installed for a limited period of time (e.g. signals in temporary bases)

terminal A handheld device used to allow engineers to communicate with equipment

TfL Transport for London

TIH Travel Information Highway

Tii Transport Infrastructure Ireland

TJR Through Junction Running

Toucan crossing A stand-alone combined crossing pedestrian/cyclist crossing

tram signal Traffic signals used with LRT's running on-street

TRANSYT Computerised traffic modelling tool for the assessment of traffic signal networks

TRL Transport Research Laboratory

TPMS Technology Performance Management system (replaced NOMAD)


UPS Uninteruptible Power Supply

USB Universal Serial Bus

UTMC Urban Traffic Management and Control

USDOT United States (of America) Department of Transport

USF WG UTMC Suppliers Forum Working Group

UTC Urban Traffic Control

UTMC Urban Traffic Management and Control


V2C Vehicle to Cloud (connected vehicles)

V2I Vehicle to Infrastructure (connected vehicles)

V2V Vehicle to Vehicle (connected vehicles)

V2X Vehicle to Everything (connected vehicles)

variable maximum green A feature used with traffic signals operating under Vehicle Actuated mode to allow the maximum green time to vary according to traffic flow (pretty much superceded by MOVA)

vehicle actuation Traffic signal mode of operation - responds to vehicle detection

VSLTR Variable Speed Limits Through Roadworks

VMS Variable Message Sign

VOSA Vehicle and Operator Services Agency (now DVSA)


wait indicator An illuminated panel in a pedestrian push button box which indicates that a demand has been registered

walk with traffic Where pedestrian phases are active at a signalised junction whilst none conflicting traffic phases are operational

washout The reduced contrast between an illuminated aspect and its background caused by the nonspecular reflection of incident light on the lens

WAVE Wireless Access in Vehicular Environments (IEEE 802.11p)

wig wag A signal having two similar aspects which are illuminated alternately

WIMS Weigh in Motion System