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Paul Evans
Traffic Control Terminology

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Average Annual Daily Traffic.

Advanced Public Transportation Systems (APTS)
The application of advanced electronic and communications technologies to improve the safety and efficiency of public transit systems. See also Intelligent Transportation Systems (ITS).

Advanced Traffic Management Systems (ATMS)
Systems using high-technology devices, on both freeways and urban streets, to more efficiently manage traffic. These include roadside sensors, ramp metering, cameras, dynamic message signs, HOV lanes and synchronized traffic signals that respond to traffic flows.

American Association of State Highway and Transportation Officials.

Abrasion (pavement markings)
A condition manifested in pavement markings by gradual surface erosion, thinning, and disappearance of the film due to wind, water, sand, and vehicle tire wear.

A rate of change of speed (km/h/sec or m/seC2) resulting in an increase in travel speed.

Acceleration Lane
A speed change lane for the purpose of:

(1) enabling a vehicle entering a roadway to increase its speed to a rate at which it can more safely merge with through traffic:

(2) providing the necessary merging distance: and

(3) giving the main road traffic the necessary time to make appropriate adjustments.

A way of entering or travelling towards a location. It is used when describing which vehicle movements may be permitted at an intersection (such as with an access-only barrier). It is also used when describing the location of driveways and walkways which provide an entrance to a property. See Egress and Ingress.

See Collision.

The operation of a detector in registering the presence or passage of a vehicle or pedestrian.

Advanced Traveller Information Systems (ATIS)
This system provides travellers with information to help in trip planning and changing course en route to bypass congestion, e.,g., broadcast traffic reports, in - car computerized maps and highway DMSS. Also can include automated transit trip planning and automated rideshare matching.

Advance Warning Area
The first component of a work zone, upstream of the approach area, used to alert drivers to road work ahead.

Advisory Maximum Speed
An advisory speed posted when the roadway geometries result in a maximum safe speed which is 20 km/h or more below the operating speed, and is 10 km/h or more below the regulatory speed limit.

Advisory Speed
The speed, determined to the nearest 5 km/h, at which traffic may safely negotiate a potential hazard under favourable driving conditions.

Automatic Incident Detection.

Air Brake
A brake in which the mechanism is actuated by the manipulation of air pressure. The term is often used to describe brakes that employ air under pressure above atmospheric, in contrast to vacuum brakes, which employ pressure below atmospheric.

All-red Interval (Traffic Signal)
The time in seconds of a red indication for all intersection traffic. It is used following an Amber Clearance Interval to permit vehicles or pedestrians to clear the intersection before conflicting traffic receives a green indication. In Temporary Conditions, the All-red Interval is used to clear a one-lane section through a work site before opposing traffic receives a green indication.

Amber Clearance Interval (Traffic Signal)
The clearance interval in which the signal indication for that Phase is amber. A clearance interval to warn approaching traffic to clear the intersection before conflicting traffic receives a green indication.

A.M. Peak Hour
The one hour in the morning when traffic volumes are highest.

A.M. Peak Period
The period (rush hour) in the morning when traffic volumes are highest

Annual Average Daily Traffic (AADT)
The total yearly traffic volume on a given road divided by the number of days in the year.

Annual Average Weekday Daily Traffic (AAWDT)
The total yearly traffic volume on a given road collected on weekdays and divided by the number of weekdays (252 or 253 days) in the year. Traffic volumes on statutory holidays are not included.

Approach Area
The second component of a work zone, downstream of the advance warning area, and upstream of the transition area, in which the driver is informed of lane changes, speed reductions, passing restrictions and the like.

Approach Nose
The end of a traffic island first encountered by a road user approaching from a given direction- also called the Upstream End. Depending on the situation, traffic may pass only to the right of the island, or on both sides. Each traffic island has two approach ends, one for each direction of travel.

Approach Speed
The maximum safe speed that can be maintained over a short section of highway immediately in advance of a potentially hazardous location, taking into account pavement and shoulder width, horizontal and vertical alignment, sight distance, and other controlling factors. The approach speed does not necessarily coincide with the Design Speed.

Advanced Public Transit Systems.
See Intelligent Transportation Systems (ITS).

Area Parking Control
A parking control plan for an area or community.

Arterial Road
A Major Road, used primarily for through traffic rather than for access to adjacent land, that is characterized by high vehicular capacity and continuity of movement. Intersections are spaced relatively far apart and are frequently signalized. See also Collector Road and Local Road.

Assurance Sign
A Directional Guide Sign or Trailblazer, providing confirmation to the travellers that they are on the desired route or road, and/or are traveling toward the desired destination.

American Society for Testing and Materials.

Area Traffic Control.

At-grade Intersection
An intersection of two roadways where there is no vertical separation between the two roadways at their point of intersection.

Advanced Traveller information Systems.

Advanced Traffic Management Systems.

American Traffic Safety Services Association.

Automatic Vehicle Identification (AVI)
Vehicles equipped with AVI transponders are identified when they come within range of a roadside communication unit. Most common application is for automatically collected tolls on toll highway: however, the system may also be used as a means of automatically collecting travel time information along freeways.

Automatic Vehicle Identification in Ontario (AVION)
A commercial vehicle electronic clearance system along Highway 401 (Windsor to Whitby) and Interstate 1-75 in the U.S.

Automatic Vehicle Location (AVL)
A system which enables the approximate location of a vehicle to be determined and tracked as it traverses the transportation network. Commonly used by emergency services and transit agencies to track location of vehicles. Also can be used to monitor traffic conditions by obtaining probe reports from vehicles travelling in the network.

Automated Vehicle Classification.

Average Daily Traffic (ADT)
The total volume during a given time period in whole days greater than one day and less than one year divided by the number of days in that time period.

Automated Vehicle Guidance.

Automatic Vehicle Identification.

Automatic Vehicle Identification in Ontario.

Automatic Vehicle Location.


Bailey Bridge

See Temporary Bridge.

Ball Bank Indicator
A mechanical or electronic device that can be mounted inside a four-wheel vehicle. Readings of the ball bank indicator show the combined effects of the body rolling angle, centrifugal force and superelevation angle to estimate the safe operating speed around a curve.

A device which provides a visual indicator of a hazardous location or the desired path a motorist should take, but is not intended to contain or redirect a vehicle. A barricade is intended to provide separation or to inform of closure, or to provide direction to pedestrians. A barricade is not a primary means of providing direction to motorists, but is supplemental to other traffic control devices providing delineation.

A device which provides a physical limitation, through which a vehicle would not normally pass, and is intended to contain or redirect an errant vehicle of a particular size range, at a given speed and angle of impact.

Base Period
See Off-peak Period.

Benefit/Cost Ratio (B/C Ratio)
A ratio used to compare the benefit versus the cost of proposed alternatives. For highway projects, benefits may include reduced fuel consumption, travel time, and air pollution costs may include construction, right of way, and maintenance.

Bicycle Facility
A general term denoting a facility with improvements and provisions made or administered by public agencies to accommodate or encourage bicycling, including bikeways and bikeway parking facilities.

Bicycle Lane
A portion of a roadway which has been designated by striping, signing and pavement markings for the preferential or exclusive use of bicyclists.

Bicycle Parking Area
A general term referring to any facility provided for parking bicycles. It can include racks, compounds, stands or lockers.

Bicycle Path
A bikeway physically separated from the motorized vehicular traffic by an open space or barrier and either within the highway right-of-way or within an

Bicycle Route
A segment of a system of bikeways designated by the jurisdiction having authority, with appropriate directional and information markers, with or without a specific bicycle route number.

Bicycle Trail
An unimproved bikeway.

Bidirectional Bikeway
A two-way bikeway.

Any road, path, or way which in some manner is specifically designated as being open to bicycle travel, regardless of whether such facilities are designated for the exclusive use of bicycles or are to be shared with other transportation modes.

Blank-out Sign
A type of CMS with two states, either on or off. When the blank-out sign is off, there is no message displayed. When the sign is on, a pre-determined message is displayed to motorists.

Blocker Truck (BT)
A Buffer Vehicle (BV) not equipped with a Truck-mounted Attenuator.

A highway section with reduced capacity that experiences operational problems such as congestion. Bottlenecks may result from factors other than reduced roadway width. For example, the close spacing of exit and entrance ramps can cause weaving patterns that result in congestion. A less obvious example is a steep freeway grade that can slow trucks and cause a localized "bottleneck."

An improved strip of land:
(1) between the roadway and the sidewalk-, or
(2) between two opposing roadways (median boulevard).

Boulevard Bikeway
A bikeway on a roadway boulevard.

Broken Line
A Pavement Marking consisting of a cycle of marking segments and gaps. Broken lines are permissive and inform drivers that they are permitted to cross a broken line, (two-lane, two-way highways or multi-lane roadways) or that there is a change in use of a particular lane (continuity lines).

Buffer Vehicle (BV)
A truck positioned in a stationary work zone or in a mobile work operation to provide buffer protection for workers against errant vehicles intruding into a work zone or mobile work operation. The generic term Buffer Vehicle refers to either a Blocker Truck or a Crash Truck. As required by OHSA, a Buffer Vehicle must have a minimum mass of 6,800 kg, and must have a mounted TC-12 flashing arrow board and four-way flashers. After January 1, 2003, all Buffer Vehicles must be Crash Trucks. Before then, a Blocker Truck may be used only where the Annual Average Daily Traffic (AADT) is known to be less than 25,000 vehicles per day, otherwise a Crash Truck must be used. For MTO contracts, additional BV requirements apply.

Built-up Area
The territory contiguous to a highway not within a city, town, village or police village where:

(1) not less than 60% of the frontage upon one side of the highway for a distance of not less than 200 m is occupied by dwellings, buildings used for business purposes, schools or churches.

(2) not less than 50% of the frontage upon both sides of the highway for a distance of not less than 100 m is occupied by dwellings, buildings used for business purposes, schools or

(3) not more than 200 m of the highway separates any territory described in clause ( 1 ) or (2) from any other territory described in clause (1 ) or (2) and signs are displayed as required.

Bull Nose
The area or point of divergence between two diverging roadways, such as between freeway mainline lanes and an exit ramp.

Business District
The territory contiguous to and including a highway when within 180 m along such highway there are buildings in use for business or industrial purposes, including but not limited to, hotels, banks or office buildings which occupy at least 90 m of frontage on one side or 90 collectively on both sides of the highway.

Bus Lane
A street or highway lane intended exclusively or primarily for buses, either all day, or during specified periods. See also Reserved Lane and Transit Lane.

Call (Traffic Signal )
A registration of a demand for right-of-way by traffic (vehicular or pedestrian) at a controller.

Call Box
A telephone or other communications device located at given locations along the side of a freeway.
Motorists can request various services (such as police fire, or ambulance, etc.) by pressing certain buttons or using voice communications.

The maximum number of vehicles which can pass over a given section of lane or a roadway in one direction, or in both directions for a two-lane or three lane highway, during a given time period (usually one hour) under prevailing roadway and traffic conditions.

An arrangement in which a group of people share the use and possibly the cost of a car in travelling to and from pre-arranged destinations together.

A bridge or raised way constructed over marshy land or water. It may be either an earth fill or bridge type structure.

Canadian Capacity Guide for Signalized (Urban) Intersections.

Central Business District (CBD)
The downtown retail trade and commercial area of a city or an area of very high land valuation, traffic flow, and concentration of retail business offices, theatres, hotels and services.

Centre Lane Facility
A reserved lane at or near the centre of a roadway.

See Directional Dividing Line.

Changeable Message Sign
A specific subset of Dynamic Message Signs which may display a limited number of fixed messages, any one of which may be displayed at any given time, or no message at all. It is an electrical, electro-optical, electromechanical, or mechanical sign which permits the sign message to be changed, either locally or remotely. See also Dynamic Message Sign and Variable Message Sign.

The separation or regulation of traffic movements into definite paths of travel by use of pavement markings, raised islands, or other suitable means to facilitate the safe and orderly movement of traffic, both vehicular and pedestrian.

Channelizing Devices
Cones, construction markers, flexible drums (barrels), pavement markings and any temporary barriers used to alert drivers to and direct traffic past hazards created by construction or maintenance activities.

Chevron Alignment Sign
A delineation sign used to delineate sharp roadway alignment changes. See Books 6, 7 or 11.

A series of Curb Extensions on alternating sides of a roadway, which narrow a roadway and require vehicles to meander to travel through the chicane. Typically, a series of three curb extensions is used.

See Curb Extension.

Closed Lane
A traffic lane on a roadway that has been closed off to traffic by either Channelizing devices, signs, temporary concrete barriers, and/or TC- 12 flashing arrow boards.

Collector Road
A road for which vehicle movement and access are of equal importance. Direct access to adjacent properties may be permitted in some cases, typically in lower density residential areas. Intersections are spaced at varying intervals and are typically only signalized where the collector road intersects an arterial road or in some cases another collector road. See Arterial Road and Local Road.

An incident resulting in property damage, personal injury or death and involving the loss of control and/ or the striking of one or more vehicles with another vehicle, a person, an animal or an inanimate object.

Colour Sequence (Traffic Signal)
A predetermined order of signal indications within a cycle.

Commercial Motor Vehicle
A motor vehicle having a permanently attached truck or delivery body, including fire apparatus, buses, and truck tractors and trailers (combination units) used for hauling purposes on the highways, and requiring a Commercial Vehicle Operating Registration (CVOR).

Commercial Sign
A sign failing into one of the following classes:

(1) field advertising
(2) third-party signs
(3) other commercial signs, on the highway right-of-way, for which a fee may be charged.

Commercial Vehicle Operations (CVO)
The application of advanced electronic and communications technologies to improve the safety and efficiency of commercial vehicle/fleet operations. See also Intelligent Transportation Systems (ITS).

The ability of drivers to understand the meaning of a sign message, including any symbols or abbreviations-

Concurrent Flow Lane
A reserved lane for vehicles on which the direction of traffic is the same as the flow of traffic on the adjacent lanes.

Concurrent Timing (Traffic Signal)
A mode of controller operation whereby a traffic phase can be selected and timed independently and simultaneously with another traffic phase.

Cone of Vision
The small three-dimensional angle of vision, measured about the axis of the eye's pupil, and from the surface of the eye, within which angle maximum visual acuity is achieved.

A Collision or near-collision which requires evasive action on the part of one or more persons. Conflicts can occur between two motorists, between a motorist and cyclist, between a motorist and pedestrian, and between a cyclist and pedestrian.

Conflicting Phase (Traffic Signal)
Two or more phases, which will cause interfering, traffic movements if operated concurrently.

Conflict Monitor (Traffic Signal)
A device used to continually check for the presence of conflicting signal indications and to provide an output in response to conflict.

Congestion Management System
A systematic process that provides information on transportation system performance and alternative strategies to alleviate congestion and enhance the mobility of persons and goods. A Congestion Management System includes methods to monitor and evaluate performance, identify alternative actions, access and implement cost-effective actions, as well as to evaluate the effectiveness of implemented actions.

The ability of a traffic control device to attract or command attention, given the visual setting in which it is placed.

All work zone activities, including pre-engineering activities, relating to the building, capital maintenance, or rehabilitation of highways or utilities along or crossing highways.

Construction and Maintenance Signs
A group of Regulatory and Warning Signs used for the protection of public traffic and workers in the vicinity of a work area located on or near the roadway.

Construction Marker
A TC-52 Channelizing Device.

Construction Zone
One or more highway work zones located on or near the roadway. A construction zone must be designated and signed in order to have enforceable maximum speed limits.

Continuity Line
A lane line of reduced spacing and increased width, designed to alert road users to an impending change in lane function. See also Wide Line.

Continuous Wide Median
On a divided highway, a median that has a continuous width of 10 m or more. See also Divided Highway.

A flow of vehicles on which the direction of traffic is opposite to the flow of traffic on the adjacent lanes.

Contra-flow Lane
A reserved lane for vehicles on which the direction of traffic is opposite to the flow of traffic on the adjacent lanes.

Contrast refers to differences in colour or in brightness which allow a target, such as a sign message or symbol, to be seen against the sign background.

Controlled Access Highway
A major highway along which the right of access to abutting property is controlled by the road authority, and where access to and from the highway is provided through interchange entrance and exit ramps.

Controlled Access Rights-of-way
Control of access is the condition where the right to access to or from a highway, by owners or occupants of abutting land or by other persons, is fully or partially controlled by the public authority.

Controlled Intersection
An intersection where traffic approaching from any or all directions is regulated by some form of traffic control device.

Controller (Traffic Signal)
The general usage term for the controller unit, cabinet and associated appurtenances.

Controller Unit (Traffic Signal)
That part of the controller which performs the basic timing and logic functions. A microprocessor-based or electromechanical timing unit.

Coordination (Traffic Signal)
The control of Controller Units in a manner to provide a relationship between specific green indications at adjacent intersections, in accordance with a time schedule to permit continuous operation of groups (platoons) of vehicles along the street at a planned speed.

A broad geographical band that follows a general directional flow connecting major sources of trips that may contain a number of streets, highways and transit route alignments.

Corridor Control
The process of managing and controlling utilities, buildings, road access, and commercial signing on the highway right-of-way and the areas on either side adjacent thereto.

Corridor Traffic Management
The process of managing and controlling traffic between/among parallel roads within a corridor.

See Collision.

Crash Cushion
A traffic barrier used to safely shield fixed objects or other hazards from approximately head-on impacts by errant vehicles, consisting of energy-absorbing elements that are progressively deformed on impact.

Crash Truck (CT)
A Buffer Vehicle (BV) equipped with a Truck-mounted Attenuator (TMA) meeting National Cooperative Highway Research Program Report NCHRP 350 requirements.

See Pedestrian Crossover.

See Pedestrian Crosswalk.

The round or circular section of the end of a dead end street.

A vertical or sloping construction element along the edge of the pavement or shoulder forming part of a gutter, strengthening or protecting the edge, and clearly defining the edge to vehicle operators. The surface of the curb facing the general direction of the pavement is called the "face".

Curb Extension
The intrusion of the curb into the roadway to reduce its width.

Curb Marking
A marking used to delineate the location of a curb.

Curb Radius
The radius of the circular curved curb which connects the tangent curb sections of intersecting streets.

A horizontal or vertical deviation in the roadway. A horizontal curve appears as a bend in the roadway, requiring drivers to turn the steering wheel. A vertical curve appears either as a "crest" or a "sag" to provide for a change in gradient on the profile of the roadway.

Curve Sign
A Warning Sign used to inform drivers of an upcoming change in roadway alignment. In some cases, a reduction in speed is recommended.

Commercial Vehicle Operations.
See also Intelligent Transportation Systems (ITS).

Commercial Vehicle Operating Registration.

When referring to a traffic signal, cycle describes one complete sequence of signal indications.

Cycle Length (Traffic Signal)
The time (in seconds) required for one complete sequence of signal indications.

Cycle Splits (Traffic Signal)
The times in percent of the cycle for the phases making up the cycle.

Cyclist Rest Area
A general term referring to a facility provided for cyclists to stop. It can include benches or picnic tables, bicycle parking facilities, trash cans, washrooms, drinking fountains, and bikeway network maps.