Knowledge Is Power

Chrisolas Management Services

Health & Safety Consultants

Knowledge Is Power

Training Courses
TCP - Flagger
TCT - Book 7
TCS - Supervisor
Traffic Plan Design
Traffic Control Plans
Safety Consulting
Industry Links
Traffic Terminology
Contact Us


Paul Evans
Traffic Control Terminology

A » C   |  D » L   |  M » P   | Q » S T » Y

A line or sequence of vehicles, etc., awaiting their turn to be attended or to proceed, in which the rate of flow from the front of the queue determines the average speed within the queue. Slow vehicles joining the rear of the queue are usually considered a part of the queue.

Queue Warning System.

Radio Detection and Ranging (RADAR)
A method of determining the location and speed of an object. Radar works by transmitting signals and measuring the time it takes for them to bounce off the targeted object and return.

All forms of non-highway ground transportation thatrun on rails or electromagnetic guideways, including-.

1) Commuter or short haul rail passenger service in a metropolitan or suburban area-, and

(2) high speed ground transportation systems that connect metropolitan areas, without regard to whether they use new technologies not associated with traditional railroads.

Railroad Crossing
A location where one or more railroad tracks cross a public highway, road, street, or a private roadway, and includes sidewalks and pathways at or associated with the crossing.

Rail to Trail
A general term referring to the conversion of an abandoned rail right-of-way to a recreational use, including bikeways.

Rail with Trail
A term referring to a path within an active rail right-of-way.

Raised Crosswalk
A marked Pedestrian Crosswalk at an intersection or mid-block, constructed to the same elevation as adjacent curbs and sidewalks.

Raised Intersection
An intersection where the elevation of the whole centre of an intersection, including the pedestrian crossing, has been raised to the same height as the adjacent curbs and sidewalks.

An interconnecting roadway of a traffic interchange, or any connection between highways at different levels or between parallel highways, on which the vehicles may enter or leave a designated roadway.

Ramp Control
See Ramp Metering System (RMS).

Ramp Metering System (RMS)
A system used on a freeway or expressway entrance ramp in which the rate of entry of vehicles onto the freeway is metered by a traffic signal, - the signal allows one vehicle to enter on each green indication or green flash. The operation of the metering signals is normally carried out only during rush hours and in a preferred direction (normally toward the Central Business District (CBD) in the morning and outbound from it in the evening).

Radio Data System - Traffic Message Channel.

Reading Time
The time required to read a sign with a given message.

Recurring Congestion
Typically predictable and occurs at locations where demand exceeds capacity, or at geometric Bottlenecks (e.g., lane drops, high-volume entrance ramps, etc.).

Red Clearance Interval (Traffic Signal)
A clearance interval which may follow an Amber Clearance Interval, intended to allow time at the end of a Phase for vehicles in the intersection to clear prior to release of a Conflicting Phase.

See Reflectivity.

A measure of the degree to which a surface reflects incident light. A related term, reflectance, is the amount of light reflected back from a sign, relative to the amount of light shining on the sign. See Retroreflectivity, Coefficient of (R).

A method of incorporating light-reflective material on the approach face of a Traffic Sign so that the face will reflect light during the hours of darkness while retaining the same colours as by day.

Refuge Island
An island provided in a street for the safety of pedestrians, either as a Median Island on a wide street, where the width may not permit pedestrians to cross the street on a single Pedestrian Signal indication, or as a loading island for transit, such as Streetcars.

Regulatory Sign
A Traffic Sign advising drivers of action they should or must do (or not do), under a given set of circumstances. Disregard of a regulatory sign would usually constitute an offence.

Remote-control Device
An electromechanical device that is remotely controlled and performs the function of a Traffic Control Person (TCP), as controlled by a TCP.

Representative Vehicle
See Design Vehicle.

The Road Emergency Services Communications Unit.

Reserved Lane
A street or highway lane reserved for use by specific classes of vehicles, either all day, or during specified periods. These classes may include any or all of buses, carpools, taxis or bicycles.

Reserved Lane Controls
All controls, including Traffic Control Devices and physical devices, intended to ensure that a Reserved Lane functions in accordance with its intended purpose.

Residential District
That portion of a municipality, or an area within the influence of a municipality, in which the dominant land use is residential development, but where small business areas may be included.

Response Time
The time between the occurrence of an event to the sensing of that event and providing an action to it.

Refers to areas where, or times when, a driver is not permitted to travel.

Rest Site
A roadside area usually having facilities for people and vehicles.

The reconstruction of a roadway or other transportation facility with physical changes to the existing design. An example of a common traffic calming retrofit is to reconstruct the curbs at an intersection to incorporate curb extensions.

Retroreflective Material
A type of material applied in either strips or sheets which reflects illumination back to its source.

Retroreflectivity, Coefficient of (R)
R indicates the proportion of light reflected back to the driver from a Retroreflective sign surface, in candelas per lux per square metre. See OTM Book 1 b (Sign Design Principles), Section 9. 1.

Reversible Lane
A lane on which the direction of traffic can be changed to utilize maximum roadway Capacity during Peak Periods.

The function of matching a ride with other passengers in a common vehicle. The term is usually applied to carpools and vanpools.

Right-in/Right-out Island
A raised triangular island at an intersection approach that prevents left turns and through movements to and from the side street.

Right-of-way (ROW)
(1) Allocation of right of movement to a road user, in preference over other road users,-

(2) The width of the road allowance from the property line on one side to the property line on the opposite side of the roadway.

Right-of-way Rule
Although these may vary in specific localities, generally a vehicle approaching an uncontrolled intersection must yield to a vehicle approaching on the leg to its right.

Right Turn on Red (RTOR)
A right-turning movement permitted on a red signal indication after coming to a stop and ensuring that a right turn can be made safely. Allowed by the HTA, but subject to site-specific local by-laws.

Ramp Metering System.

Road Authority
The body (Municipal, Provincial or private) that has legal jurisdiction over a roadway.

Road Closure
The closing of a highway to road users. Road closures are covered by Regulation 599 of the HTA.

Road Edge Work
Construction, maintenance, or utility work that encroaches on the edge of the road, with much of the work being done on the shoulder. Road edge work is not fully on the shoulder, nor does it result in a remaining travel lane width of less than 3.0 m (3.5 m on freeways), which would necessitate a lane closure or a Partial Lane Shift. See also Roadside Work.

Roadside Diversion
A deviation of the normal roadway, essentially within the highway right-of-way, where traffic is required to make a short diversion to bypass the work area. The diversion must be signed, using a TC-9, TC-16, and/ or other appropriate signs.

Roadside Work
Construction, maintenance, or utility work that is done on the shoulder or on the edge of the road. Roadside Work includes both work on the shoulder and Road Edge Work.

The part of the highway that is improved, designed or ordinarily used for vehicular traffic, but does not include the Shoulder, and, where a highway includes two or more separate roadways, the term "roadway" refers to any one roadway separately and not to all of the roadways collectively.

Roadway Alignment Sign
A Warning or Temporary Conditions Sign used to inform drivers of an upcoming change in roadway alignment, including turns and Curves.

Roadway Edge Line
See Edge Line.

Roadway Pavement Marker
A ceramic, metal, glass or plastic marking device placed on or in the roadway to substitute for or act as a supplement to standard pavement markings. Roadway pavement markers are comprised of a variety of configurations including Retroreflective and non-Retroreflective markers, and markers that employ prismatic retroreflection and those that employ spherical retroreflection.

A raised circular island located in the centre of an intersection, which requires vehicles to travel through the intersection in a counter-clockwise direction around the island. Roundabouts are typically used on arterial and collector roads, and are distinguished by YIELD signs and raised Median Islands on all approaches, and in some cases, gradual widening of the entry approach to two or more lanes.

Route Detour
A detour where a driver is required to depart completely from the normal route and is directed to use an alternate route. The alternative route must be signed using a combination of the appropriate TC-10 directional signs. Prior to the closing of the roadway and the opening of a detour, a TC-65 'Road Closing Notice" sign must be erected at strategically selected locations of the road at least one week in advance of the actual closing.

Route Marker
A Guide Sign bearing a route number which is erected along numbered highways.


Roadway Pavement Marker.

A term used to describe drivers who slow down and gape inquisitively at an incident or accident, often causing congestion problems.

Rumble Strip
Raised buttons, bars or depressions closely spaced at regular intervals on the roadway or shoulder that create both noise and vibration in a moving vehicle to alert the driver or cyclist of an upcoming situation, or of a potentially hazardous deviation from the normal travel way. Also called Singing Strip.

Rural Area
An area outside of the limits of any incorporated or unincorporated city, town, village, or any other designated residential or commercial area.

Rural Bikeway
Any Bikeway that is not an Urban Bikeway.

Road Weather Information Systems. Spacing of Delineators on curves.

Safe Speed
See Advisory Speed

Safe Stopping Distance
The distance required to bring a vehicle completely and safely to rest with normal braking and road conditions.

SCATS (Sydney Coordinated Adaptive Traffic System)
SCATS gathers data on traffic flows in real-time at each intersection. This data is fed via the traffic control signal box to a central computer. The computer makes incremental adjustments to traffic light timings based on minute by minute changes in traffic flow at each intersection. SCATS performs a vehicle count at each stop line, and also measures the gap between vehicles as they pass through each junction. As the gap between vehicles increases the lights are wasting green time, and SCATS seeks to reallocate green time to where demand is greatest.

SCOOT (Split Cycle Offset Optimization Technique)
SCOOT is a dynamic, on-line, real-time method of signal control that continuously measures traffic demand on all the approaches to intersections in a network and optimizes the signal timings at each intersection to minimize delay and stops. Timing changes are small, to avoid major disruption to traffic flows, and frequent, to allow rapid response to changing traffic conditions..

School Bus
Any bus which is used for the express purpose of transporting students to and from school. Ontario registered vehicles must be Chrome Yellow in colour.

School (and Pedestrian) Signs.
A group of signs, both Regulatory and Warning, used to control vehicles and protect pedestrians wherever students and pedestrians are likely to be present and conflict with vehicles may occur.

School Zone
A roadway section with a mandatory 40 km/h maximum speed zone in effect every school day at designated times, in the vicinity of a school. The HTA also makes provision for 60 km/h speed zones on King's Highways.

Self Enforcing
A traffic control measure which does not require police enforcement in order to be effective. This is often used to describe Traffic Calming Measures. A Speed Hump is self-enforcing, for example, whereas a posted Speed Limit is not.

Semi-actuated (Traffic Signal)
Operation by a type of traffic-actuated controller in which means are provided for traffic actuation on one or more but not all approaches to the intersection.

A device that measures or detects a real world condition, such as motion, heat or light and converts the condition into an analogue or digital representation. See also Optical Sensor.

Separate Roadway
A physically separated, access controlled, HOV priority treatment facility, usually located within the median of an urban freeway. Separated roadways can be either reversible or two-way, single or multi-lane facilities.

Service Life (Pavement Marking)
The time required for a pavement marking to become ineffective due to its having lost its luster, lost its Retroreflectivity, or having been worn completely from the pavement.

Means the same as "must".

Shared Roadway
Any roadway upon which a Reserved Lane is not designated and which may be legally used by a variety of vehicle types regardless of whether such facility is specifically designated. This includes bicycles, buses, taxis, and carpools.

The use by traffic of Neighbourhood or Local Roads in order to bypass congestion or an obstruction on the Arterial or Collector Road network.

Short Duration (SD) Work
Stationary maintenance, construction, or utility activities which require a separate work space, which are continuously attended by workers, and which are more than 30 minutes and less than one 24-hour period in duration. Under certain conditions (see Section 1.8), work at the same location may be extended to more than one day, and still be considered SD work. See also Long Duration (LD) and Very Short Duration (VSD) Work.

Indicates an advisory condition. Where the word should" is used, the action is advised; recommended but not mandatory. This term is meant to suggest good practice in most situations but also to recognize that in some situations, for good reasons, the recommended action cannot or need not be followed.

The portion of a Highway between the outer edge of the roadway and the Curb, or point of intersection of the slope lines at the outer edge of the roadway and the fill, ditch, or median slope, for the
accommodation of stopped vehicles, for emergency use, and for lateral support.

Shoulder Bikeway
That portion of the road not normally used for motorized vehicular traffic, but paved for the use of bicycles as a separate Bicycle Lane, Bicycle Route or shared use lane.

Side Road (Traffic Signal)
The roadway approach or approaches at an intersection normally carrying the least volume of vehicular traffic. (Also called Minor Road.)

That portion of a road, adjacent to the travelled roadway, which has been improved for the use of pedestrians.

Sidewalk Bikeway
Any sidewalk of adequate width designed and/or striped to permit cyclists to share the travel right-of-way with pedestrians.

Sidewalk Extension
The sidewalk is continued across a local street intersection at its normal elevation, with the local street being raised to the level of the sidewalk at this location.

Sight Distance
The distance visible to the driver of a passenger vehicle, measured along the normal travel path of a roadway, to the roadway surface or to a specified height above the roadway, when the view is unobstructed by traffic.

A Traffic Control Device mounted on a fixed or portable support which conveys a specific message by means of symbols or words, and is officially erected for the purpose of regulating, warning, or guiding traffic.

The physical form of the data or message carried by the communication channel.

Signal Actuation
See Actuation.

Signal Indication (Traffic Signal)
The illumination of one or more lenses in a signal head which conveys a message to traffic approaching the signal from one direction.

Signalized Control
The use of a traffic signal control device to control traffic on a road section or intersection.

Sign Assembly
Any Traffic Sign mounted and erected alone or in conjunction with any combination of associated Tab Signs.

Sign Blank Number
The number given to a given size of standard sign blank (substrate), for purposes of identification, inventory and fabrication.

Sign Pattern
The full-size drawings of individual signs, showing sufficient detail and dimensional accuracy for sign fabrication.

Sign Sheeting
The Retroreflective Material used on the surface of a Sign to provide good daytime and nighttime visibility.

Sign Support
The physical means of holding a sign in its intended position.

Sign Symbol
A pictogram, depiction, arrow, silhouette or figure, and/or lnterdictory or Permissive Symbol, used to simplify or represent a word message on a sign.

Sign Truck
A vehicle that has:

(1) Four-way flashers and a mounted flashing arrow board sign, or

(2) a portable trailer with a mounted flashing arrow board sign.

Singing Strip
See Rumble Strip.

Single Axle Weight
The total weight transmitted to the roadway by all wheels whose centres may be included between two parallel transverse vertical planes 1 m apart, extending across the full width of the vehicle.

Slave Controller (Traffic Signal)
A slave controller is an intersection traffic signal controller which is locally programmed to suit the interval times required at the intersection but which is set on the phasing and timing of the system as determined by the Master Controller or Central Computer.

A motorized vehicle solely designed to operate on snow or ice.

Snow Route
A highway where parking is prohibited for purposes of snow removal as decreed by municipal by-law.

Solid Line
A continuous Pavement Marking. Solid lines are restrictive: drivers are being informed that they are not to cross a solid line.

Single Occupant Vehicle.

Special Travellers Information Sign
Signing on the highway directing drivers to particular traveller services other than tourism-related attractions and food, fuel and accommodations, such as police, airports, ferries. A sign fee may be charged for installation of these signs.

Speed Bump
A raised pavement area that extends transversely across the travel way. Speed bumps generally have a height of 0.075 m to 0. 10 m and a length of 0.3 m to 0.9 M.

Speed Change Lane
A tapered auxiliary traffic lane used by traffic entering or leaving a freeway or expressway for the purpose of acceleration or deceleration respectively.

Speed Controls
Speed zoning, enforcement, and non-enforcement measures to control speeds.

Speed Hump
A raised pavement area that extends transversely across the travel way. Speed humps generally have a height of 0.08 m and a length of 4 m to 7 m.

Operating at a speed, possibly below the posted limit, above that at which a reasonable and prudent person would operate under the circumstances, or operating at a speed above the legal limit.

Speed Limit
The maximum vehicular speed allowed within any given posted or unposted Speed Zone.

Speed Variance
A measure of the range of speeds chosen by drivers. It is usually measured as the difference between the 15th and 85th Percentile Speeds.

Speed Zone
A specific section of roadway upon which a maximum speed limit has been imposed. Such zones may be posted or unposted. A construction speed zone must be posted.

Split (Traffic Signal)
For an actuated Controller Unit, a division of the Cycle Length allocated to each of the various phases (normally expressed in percent). For a pretimed controller unit, split is the time allocated to an Interval.

Spot Speed Study
A vehicle speed study taken at a stationary location.

Staged Freeway
A highway designated as a possible future freeway, being constructed by stages with either two or four lanes and with both At-grade Intersections and Interchanges. One consequence of the staged freeway designation is the restriction on Field Advertising.

An individual or organization with an interest in transportation issues generally, or in a neighbourhood or specific location.

A rule, principle, pattern or measure, which practice or theory has shown to be appropriate for a given set of conditions, and applicable, as the case may be, to planning, design, traffic control devices, operations or maintenance.

The halting of a vehicle whether occupied or not, except for the purpose of and while actually engaged in the receiving or discharging of passengers.

Statutory Speed Limit
A maximum speed limit automatically in effect on all roads, unless otherwise signed. The statutory speed limit applies even where no maximum speed limits are signed.

Steep Hill
A downgrade of 6% or more.

Stop Bar
A Pavement Marking placed laterally across the approach half of a travelled roadway at the site of a STOP sign, Traffic Signal, or Pedestrian Crosswalk. The line indicates the point beyond which the foremost part of a vehicle must not protrude, should the vehicle be required to stop. Also called Stop Line.

Stop Line
See Stop Bar.

The halting of a vehicle, even temporarily, whether occupied or not, except where necessary to avoid conflict with other vehicles, or in compliance with the directions of a police officer or Traffic Control Signal.

Stopping Sight Distance
The distance required by a driver of a vehicle, travelling at a given speed, to bring the vehicle to a stop after an object on the roadway becomes visible. It includes the distance travelled during the Perception-reaction Time and the vehicle braking distance.

An urban highway.

An electrically powered rail car that is operated singly or in short trains in mixed traffic on track in city streets. See also Light Rail (LRT).

A means of enhancing the pedestrian environment through the use of physical features which provide protection, coherence, security, convenience, community identity, way-finding and orientation, aesthetic quality and interest along the main street.

A self-contained marking system mounted on a truck chassis and used to apply Pavement Markings on the road.

The surface to which the sign sheeting is applied.

Suburban Area
An area, primarily residential, generally located between an urban centre of a community and the surrounding rural area.

Superelevation Rate
The rate of rise in cross section of the finished surface of a roadway on a curve, measured from the lowest or inside edge to the highest or outside edge.

The top of the pavement material, Substrate, or Sign Sheeting.

Symbol Marking
A Pavement Marking used in a specific location to guide, warn, regulate, or inform road users where standard pavement markings are not sufficient.

System (Traffic Signal)
A traffic signal system is composed of a number of traffic signal controllers operating from electronic instructions given by a Master Controller at one of the intersections or given by a Central Computer at a traffic control/operations centre. A system may be installed on a single roadway with one master controller and one or more Slave Controllers or on a grid of roadways using either a master controller or a central computer. A system may use interconnection methods or telephone or cable television networks or any combination thereof for the transmission of data commands to the local slave controllers.