North American
Light Rail Terminology
Updated June 7, 2008
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
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Absolute Block
- A block that, by design, must not be occupied by more than one train.
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Accident
- An unforeseen event or occurrence, which results in injury or property damage.
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Accident, Preventable
- An occurrence involving rail equipment or personnel which results in property damage or
injury that could have been prevented by the proper application of Rules or Procedures or
by reasonable action by persons involved.
-
AC (Alternating Current)
- Used by local utilities to deliver electrical power to substations. Also used by
lightrail vehicles for HVAC, other utilities and sometimes for motive power.
The elementary explanation is as follows: In AC systems, the flow of electricity Alternates or
reverses frequently (the frequency, expressed in cycles, Hertz, Hz, etc.). In comparison
to DC (Direct Current), AC can be transmitted long distances with little loss of voltage, and can easily have its voltage transformed.
-
ADA (Americans with Disabilities Act)
- A 1990 Federal law that mandates specific requirements for vehicles and facilities,
such as stations and terminals to accommodate the disabled.
-
Adds/Cuts
- A term that refers to the act of changing the number of cars within a
consist
while on the
Main Line.
-
AFC (Automatic Fare Collection)
- The first system, for the Illinois Central Chicago suburban district was (and still is)
called ARCS, for Automatic Revenue Collection System.
-
AFO (Audio Frequency Overlay) Circuit
- A track circuit system that uses audio frequencies to detect train location and
direction. Several audio "loops" are embedded in the track allowing the system to detect
the direction of approach of a train to a particular location such as a grade crossing.
Generally used to activate gates or support data collection by SCADA systems.
-
Alignment
- Refers to both horizontal and vertical placement of the tracks within the corridor. The
horizontal alignment refers to the location of the railroad as described by curves and
tangents. The vertical alignment refers to the vertical
orientation of the rail. (i.e. below grade, at grade or above grade).
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Allocation
- A method for dividing federal funds among states when no apportionment formula exists
for that money.
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ALRT (Automated Light Rapid Transit)
- A term used to describe systems that do not require the LRV operator to perform any function other than in an emergency situation, similar to the Scarborough line in Toronto or Green Line in Los Angeles. Both of these systems were designed to be driverless, but public sentiment prohibited it from occurring.
-
ALRV (Articulated Light Rail Vehicle)
- A term first used to refer to the articulated LRVs delivered to the
Toronto Transit Commission in 1983.
Used in some countries to refer to any articulated LRV.
-
APM
- Automated People Mover
-
APTA (American Public Transportation Association)
- APTA is a national, nonprofit trade association
representing the public transit industry. APTA (to quote their Mission Statement)
"serves and leads its diverse membership through advocacy, innovation, and information
sharing to strengthen and expand public transportation". APTA sponsors several yearly
events including a Bus Rodeo; a Rail Rodeo, and several Mass Transit conferences.
See the APTA web site for event details.
-
ARCS
- Automatic Revenue Collection System. (See AFC)
-
Aspect
- The combination of color and position of a fixed signal, light or lights, which provides
an indication to the train operator.
-
ATC (Automatic Train Control)
- Train movement controlled outside of the train, usually from the Control Room.
-
ATD (Average Travel Distance)
- Used by Transportation planners to compute anticipate ridership. For postwar U.S. light-rail lines, ATD derived from National Transit Database statistics falls in the range of five to seven miles. Except when the rail line is very short (Newark), or plays a major downtown-distribution role (Boston), ATD carried by rail is always greater than that carried by buses in U.S. cities. Rail services attract a greater proportion of longer-distance passengers owing to higher speed. In Portland in 1998, Light Rail ATD was 5.3 miles compared to 3.7 miles for buses.
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ATOR (ATR or A.T.O.R)
- Above Top Of the Rail. The top of the running rail of a rail system. Measurements of platforms and cars are based upon this standard measurement to determine platform and car heights.
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ATP (Automatic Train Protection System)
- A system by which train-mounted equipment is activated by a coded frequency signal that is transmitted through the rails and received by the train. These signals are interpreted by the on-board cab signal equipment to control train speed. Provisions are usually provided to allow system override to allow a train to bypass a red/stop signal with authorization from the control center.
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ATR
- See ATOR.
-
ATS (Automatic Train Stop)
- A system designed to prevent trains from entering an unsafe or unauthorized area by taking control of the train and bringing it to an irretrievable stop, whenever the train enters a block without a clear aspect. ATS systems are usually only able to be utilized in sections of track controlled by ABS.
- A device so designed and installed that, should the operator permit a train to pass a signal indicating "stop", there will be an automatic application of the brakes, which cannot be released until the train is brought to a stop.
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Automatic Block Signal
- A block signal that is activated either by track circuit or in conjunction with interlocking or controlled point circuits. This block signal automatically indicates a track condition and block occupancy.
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ATP (Automatic Train Protection)
- A system for assuring safe train movement by a combination of train detection, separation of trains running on the same track or over interlocked routes, overspeed prevention, and route interlocking.
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Auxiliary Track
- A center track, side track or tail track used for:
- Passing
- Storing
- Turning back trains
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Ballast
- The crushed rock utilized as a base for the purpose of holding the track in alignment
and profile.
-
Ballast Curb
- A longitudinal timber or structure placed or constructed along the outer edge of the floor of the ballast deck to retain the ballast.
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Batter
- The deformation of the surface of the head of the rail.
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Berthing Point
- The space designated for a train of given length to occupy when it is stopped at a station platform, in a terminal, or at some other designated place.
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Black Rail
- A condition that exists in the early mornings when dew forms on the rail head. This condition usually occurs during the fall when the days are warm and the nights are cold and wet. Black rail usually causes a
Spin-Slide condition.
-
Block
- A section of track of defined limits for train movement, the use of which is governed by:
- Rules
- Block Signals
- Cab Signals
- Rules or Instructions
- Any combination of the above
-
Block Signal
- A fixed signal at the entrance of a block to govern trains entering and using that
block.
-
BLS (Blue Light Station)
- A set of devices including breakers, lamps and communications links, used to assist emergency responders in determining sections of the OCS which are energized. Normally located at passenger stations and/or along the right of way (usually at entrance to and inside tunnels and other structures).
On some systems, a steady lamp indicates the third rail (or overhead wire) is electrified, a flashing lamp indicates the power is off. In an emergency, transit and emergency response personnel can also use the BLS to deactivate traction power at stations, although this is generally done through the control center. Due to the possible bridging of isolators by a
pantograph in adjacent areas, all electrical wires should be considered energized until grounded by qualified personnel.
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Blue Flag/Blue Signal
- A portable clearly distinguishable blue light, flag or marker placed on or near each end of an LRV or other rail vehicle to protect it from being moved energized or coupled to another LRV or rail vehicle.
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Brake, Dynamic
- A braking mode that uses traction motors, operating in reverse (as generators) to
provide a controlled braking effort to the LRV.
-
Brake, Emergency
- An irreversible slowing and subsequent stopping of the LRV activated by a depression of
the Emergency Brake (usually a medium to large red button) on any cab of an LRV. Emergency Braking utilizes friction and track braking systems ONLY and does NOT provide the maximum braking forces, as dynamic braking and Anti-Lock braking systems are not utilized.
-
Brake, Friction
- A braking system that applies stopping forces by the use of brake discs. The brakes are
normally applied by spring action and released by hydraulic or compressed air.
-
Brake, Maximum
- Maximum braking is attained through the use of controlled combination of Dynamic, Friction and Track Brakes, in addition to the use of sand placed between the rail and tires.
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Brake, Normal Service
- Friction and Dynamic braking normally used by the Train Operator to slow and/or stop the
LRV.
-
Brake, Track
- An electromagnet, usually located between wheels of trucks that when activated causes
friction due to direct contact with the rail, slowing the LRV. Track Brakes are usually activated by the Control Voltage of an LRV.
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Branch Line
- The secondary line or lines of a rail system.
-
Broken Base
- A break in the base of the rail.
-
Bumping Post
- A structure attached to the tracks at the end of a section of tracks to prevent
LRVs from leaving the tracks or entering tracks placed out of service. Bumping posts (or bumpers) are also used for heavy rail, commuter rail, and freight rail lines.
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Cab
- The operating compartment of an LRV from which a consist is controlled. All LRVs (except
CLRVs, ALRVs used by TTC and Kawasaki cars,
used by Philadelphia) have two cabs per car. Cars with one cab are described as
single-ended LRVs, those with two cabs are double-ended LRVs.
-
Cab Pass
- In systems that allow riders in the operating cab of a train, a cab pass identifies the
holder of the pass as a person allowed to ride in the cab of the train by management.
Cab Signal System
- A signal system whereby block condition and the prevailing civil speed commands are transmitted and displayed directly within the train cab. The cab signal system may be operated in conjunction with a system of fixed way-side signals or separately.
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Cab Signal
- A signal located in the driver's cab, transmitted through a
TWC
system, indicating a condition affecting the movement of the train, and/or displaying the
specified track speed. Cab signals are used in conjunction with
interlocking signals and in conjunction with or in lieu
of Block Signals.
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Catenary
- Overhead wires of a
TES that contain both
messenger and contact wires.
-
CBD (Central Business District)
- A term used in by transit professionals, urban planners, and/or the public to describe North American cities' Downtown area (e.g. Austin, Dallas,
New Orleans, Portland and others).
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CBTC (Communications-Based Train Control)
- A system whereby wayside radio-frequency communications with on-vehicle responder devices replaces track-circuit systems.
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CCU (Communication Control Unit)
- The unit that controls communications between cars in a
consist.
-
CFM (Cubic Feet per Minute)
- Used by tunnel planners to calculate movement of air into/out of a tunnel.
-
CLRV (Canadian Light Rail Vehicle)
- A term referring to the
LRVs delivered to
TTC (Toronto Transit Commission) in
1978. These vehicles were a European design, built in Thunder Bay, Ontario. These vehicles
do NOT have couplers and operate in single car consists.
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Coast
- A position on the
master controller in which neither
power or braking is requested.
-
Consist
- A train consisting of one or more cars.
-
Control Voltage
- An LVPS (Low Voltage Power System), usually 12-36 volts, used to control all functions
of the
LRV. Control Voltage systems have batteries as a back-up
system. The LVPS usually operates 1 hour without a charge, allowing
the LRV to operated to a safe location for storage prior to repair.
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Controller
- A light rail employee, usually located in a control room environment, that controls the
movement of an LRV within a system, maintains radio communication with all support staff, and monitors
SCADA and related equipment. Controllers are usually more experienced train operators and/or supervisory employees. Controllers are the staff that train operators look to for advice or direction when abnormal situations occur within a system.
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Contact Wire
- The lowest wire of the
OCS. The wire that provides power through
direct contact with the pantograph or trolley pole.
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Control Center
- A specific location where the Controller is located.
-
Coupler
- A device for making electrical, mechanical and pneumatic connections between
LRVs and/or other rail equipment.
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Community Re-Development
- Areas of a city, usually urban areas, designated to be ‘improved’. Tax breaks are often given to business’s, which will locate in these areas.
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Crew Key
- Refers to a specific key (most systems use the same crew key for different cars within
the fleet, but keys are usually different between systems) that allows employees egress to
cabs and cabinets within the car.
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Crossing
- A structure, used where one track crosses another at grade, and consisting of four
connected
frogs.
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Crossover
- Special track work including two switches and trackwork that allows trains to be routed
from one track to another. Wooden ties must be used under all special trackwork due to the
possibility of damage to concrete ties by lateral forces of the train. Additionally,
wooden ties are used in special trackwork, as many different lengths and shapes are needed
to accommodate the diverging rails, the economy of making these in quantity is
significantly increased.
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Cross-passage
- Within a tunnel, a passageway, usually numbered in sequential order, connecting two or
more bores of the tunnel and/or the exterior of the tunnel.
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Crushed Head
- A "flattening" or crushing down of the head of the rail.
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Current of Traffic
- The movement of trains on a main track, in one direction, specified by the rules.
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CWR (Continuous Welded Rail)
- The running rails are welded together to form a continuous rail resulting in a smoother
and quieter ride.
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DBOM (Design, Build, Operate, and Maintain)
- A project where one contractor is paid to Design, Build, Operate and Maintain a system
for a pre-determined number of years.
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DC (Direct Current)
- Direct Current is used to deliver power to light rail vehicles. Once delivered, some
lightrail vehicles convert (using a Motor Alternator) or invert (using an inverter) the DC
power to AC to use for motive or auxiliary power
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Deadman
- A device that is held or depressed by the light rail train operator that, when released,
automatically applies the brakes within a specified time period (usually 2-5 seconds).
-
De-Energize
- The act of removing electrical power from any electrical component.
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Derail
- See
Derailment
-
Derailer
- A device used to cause a derailment of rail equipment. Except in emergencies, derailers are only mounted in locations that would derail a on-track vehicle prior to entry into a work zone or other are where train movement is unauthorized.
-
Derailment
- A condition that exists when the wheel of any piece of rail equipment leaves the rail.
See Mid-Car Diversion
-
DLRT (Diesel Light Rail Transit)
- Used infrequently to describe systems using Diesel powered Light Rail Transit vehicles, such as the
Regio Sprinter.
-
DMU (Diesel Multiple Unit)
- DMU is a relatively recent evolution of the old term 'MU'. The old term was exclusively
used for self-propelled electric cars that could run in trains of two or more cars with
just one motorman. After the evolution, DMU and EMU were used to refer respectively to
diesel or electric cars. There are three major diesel-electric (non-FRA Tier 1 compliant)
DMUs in production:
-
Diverge
- A change in train movement from one track to another over a switch set in a reverse
position.
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Double Track
- A term used to describe the type of track system used on the majority of LRT systems.
Each track is separate and carries an
LRV in one direction. When
double tracks are used, tracks are usually delineated as:
- Inbound/Outbound
- Northbound/Southbound
- Eastbound/Westbound
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DSTT - Downtown Seattle Transit Tunnel
- The underground tunnel in Downtown Seattle. Most locals simply call it "the tunnel".
Currently, the DSTT tunnel is used by dual-mode (diesel and electric) Breda buses and Light Rail Vehicles. The tunnel was previously called by the acronym: DSTP, referring to it as the Downtown Seattle Transit Project.
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Dwarf Signal
- A signal placed in a significantly lower elevation that others in the system.
-
Dwell Time
- The total elapsed time from the time that a train stops in a station (usually for the
purpose of discharging and loading passengers) until the time it resumes moving.
-
Dynamic Braking
- A braking system in which the train motors acting as generators provides braking forces
upon the car.
-
EA (Environmental Assessment)
- Formerly called EIS/AA, for Environmental Impact Statement/Alternatives Analysis.
Generally, as the environmental impact of a typical transit project is benign, the more
important portion is the Alternatives Analysis. This is from the National Environmental
Policy Act. Today, since ISTEA, an EA is called a Major Investment Analysis or Major
Investment Study.
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ECU (Electronic Control Unit)
- The computer that controls all electronic functions and operations of the train. Each
car in a consist has it's own ECU, which communicates with the other ECUs in the consist.
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Effective Securing Device
- A device applied to secure a manually operated switch or derail for the protection of Roadway Workers. The device must be vandal and tamper resistant, and designed to be applied, secured, uniquely tagged and removed only by the class, group or craft of employees for whom the protection is provided.
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EIR (Environmental Impact Report)
- An Analysis of the impact that a proposed development, usually industrial, will have on the natural and social environment. It includes assessment of long and short term effects on the physical environment, such as air, water, and noise pollution, as well as effects on employment, living standards, local services, and aesthetics. The National Environmental Policy Act of 1969 as well as many state and local laws enacted during the late 1960s and early 1970s mandate that these statements be completed before major development projects can begin.
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EIS (Environmental Impact Statement)
- The Federal form of the EIR. Because the EIR and EIS are so similar they are often combined in a single document known as the EIR/EIS. An EIR/EIS usually must be conducted and approved before federal funding will be awarded.
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Electric Switch Lock
- An electrical device that locks a track switch in a position and prevents the movement
of the switch until the lock is electrically unlocked.
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Embedded Track
- Rail that has been embedded in the roadway, street, or walkway.
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Emergency
- A condition, situation or occurrence of serious nature, developing suddenly and
unexpectedly and requiring immediate action.
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Energize
- The act of turning on electrical power to a component or system.
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Exclusive Right of Way
- The placement of LRT tracks with a grade separation
from normal street traffic. LRVs are able to operate at significantly higher speeds in areas of AN exclusive right of way.
See also: Median/Side Running,
Semi-Exclusive Right of Way and
Street Running.
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Extra Train (Extra Train)
- A train not authorized by a timetable schedule. Trains used for passenger transport and
work crew may be designated as "extras".
-
Fail-Safe
- A characteristic of a system which ensures that any malfunction affecting safety will cause the system to revert to a state that is known to be safe.
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Fallback
- A scenario where a train operator leaves the end of the line with a different consist
than he/she arrived with. Fallbacks may be scheduled in advance (to reduce the number of
trains required to provide service on a line) or non-scheduled (due to one side of two sided
platform at the end of the line being out of service due to an
LRV or MOW problem).
-
Feeder
- A wire used to transfer electrical power from the to the OCS. On newer systems, these
wires run underground from the substation to the feeder pole.
-
Feeder Pole
- A TES pole that houses the feeders. Usually multiple feeders are routed from the
underground conduit to the OCS inside feeder poles.
-
FFGA (Federally Funded Grant Agreement)
- FFGA - Federally Funded Grant Agreement: Funds in which the Federal government will grant to local agencies to construct infrastructure projects.
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Fish-Plate
- A short piece of steel, lapping a rail joint, secured to the side of two members,
to connect them end to end.
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Fixed Signal
- A signal at a fixed location that affects the movement of a train.
-
Flag
- A device used for indicating a condition on the right-of-way.
-
Flair
- A tapered widening of the flangeway at the end of the guard
line of a track structure, as at the end of a guard rail or at the end of a
frog or crossing wing rail.
-
Flangeway
- The open way through a track structure, which provides a passageway for wheel flanges.
-
Flangeway Depth
- The depth of the wheel flange passageway.
-
Flangeway Width
- The distance between the gauge line and the guard line of a track structure, which
provides a passageway for wheel flanges.
-
Fouling Point
- The closest point to which a car may approach a switch from the trailing direction
without being in danger of collision with a train passing through the switch on another
track. In ABS or signalized areas, the closest point to which a car
may approach the insulated rail joint or vehicle detector governing occupation of the
block in which the switch is situated.
-
Fouling Point Marker
- The marked location on a track beyond which vehicle movement or storage of a rail
vehicle will interfere with vehicle movement on another track.
-
FRA (Federal Railway
Administration)
- Regulates all trackage within the general railroad system within the Unites States. Also
provides track specifications used on Light Rail systems. The FRA has little to no control
over Light Rail systems, except where trackage is in common with rail systems connected to
the nationwide railway system.
-
Freight Mode
- A specific mode, that when activated, allows freight operations on a Light Rail
right-of-way. A number of Light Rail systems have freight trains may
operate on or through the LRT system at designated times (usually late nights). Systems
that operate both freight and light rail vehicles are under the oversight and regulation
of FRA and FTA.
-
Friction Braking
- See
Brake, Friction
-
Frog
- A track structure used at the intersection of two running rails to provide support for
wheels and passageways for their flanges, thus permitting wheels on either rail to cross
the other.
-
FTA (US Federal Transit Administration)
- Funds and regulates mass transit within the United States previously the
UMTA.
-
Gauge (Tool)
- A device by which the track gauge is established or measured.
-
Gauge (Track)
- The distance between gauge lines, measured at right angles
thereto (Standard gauge is 4 foot 8 1/2 inches).
-
Gauge Line/Gauge Side of a rail
- A line, 5/8 of an inch, below the top of the center line of the head of running rail or
corresponding location of tread portion of other track structures along that side which is
nearest the center of the track. (In short - The side closest side to the other rail on a section of track.)
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Grade
- The ratio of rise, or fall, of the grade line to its length.
(Note - The term "Grade" is sometimes used to designate the finished roadbed, but such
use conflicts with the meaning of "Grade" as given above and it should not be so used.)
-
Grade Crossing
- A crossing of the track at grade (or street) level over a roadway. Grade Crossings are
not necessarily protected by automatic warning devices.
-
Grade Line
- The line on the profile representing the tops of embankments and the bottoms of cuttings
ready to receive the ballast; and is the intersection of the plane of the roadbed with the
vertical plane through the centerline.
-
Grade Separation
- A method of separating the tracks from the ground surface. The use of a subway, bridge,
cut, fill, or large physical barrier (or any combination thereof) to separate the traffic
of a railroad from a street, highway, pedestrian walkway or another railroad. Fencing does
not necessarily (by itself) constitute a grade separation.
-
Gradient
- The rate of inclination of the grade-line from the
horizontal.
-
Ground Strap
- A device including a wire attached to the contact wire and the railhead during
emergencies or work that will insure workers or emergency personnel's safety while working
on or around the
OCS. All overhead wires should be considered to be
energized until a ground strap is installed.
Grooved Tie
- A cross tie, which has been machine-gouged across its top depressions into which ribs on
the bottom of the tie plate may fit.
-
GPS (Global Positioning System)
- A product of military technology that allows vehicles' locations to be constantly
monitored to within meters of their actual position.
-
Guard Line
- A line along that side of the flangeway, which is nearest the center of the track and at
the same elevation as the gauge line.
-
Guard Check Gauge
- The distance between
guard line and
gauge line, measured across the track at right angles to the
gauge line.
-
Guard Face Gauge
- The distance between gauge lines measured across the track
at right angle to the gauge line.
-
Guard Rail
- A rail or other structure laid parallel with the running rail of a track to prevent
wheels from being derailed; to hold wheels in correct alignment to prevent flanges from
striking the points of turnout or crossing frogs or the points of
switches; or to keep derailed wheels adjacent to the running rails. A Guard Rail is a
passive rail and is designed to not be in contact with the inside of the wheels.
A Restraining Rail is an active rail and is designed
to be in constant contact with the inside of the wheels.
-
Guard Timber
- A longitudinal timber placed outside of the track rail, to maintain the spacing of ties.
-
Hanger
- A vertical fitting suspending the contact wire from the
messenger wire.
-
Hazard Analysis
- An analysis performed to identify hazardous conditions for the purpose of their elimination or control.
-
Hazardous Condition
- Any condition that may endanger human life or property. It includes unacceptable hazardous conditions
-
Headway
- The scheduled time separation between two trains. This term is believed to originate
from a reference to the time interval (arrival times) between the "heads" of individual
trains.
-
High Block
- A "raised" section of a station platform allowing wheelchairs (and sometimes strollers) to easily board LRVs that are 36" above top of rail. Salt Lake City, Denver and Sacramento are some of the North American systems that use high blocks.
-
High-Floor Cars/Boarding
- A system where stations are level with the floor of the cars. Floors of high-floor
boarding cars are usually 1 meter Above Top Of the Rail. High floor
cars/boarding allows wheel-chair assisted passengers to easily board trains without the use
of car or station mounted lifts. See also Low Floor Cars/Boarding.
-
High Rail Vehicle
- A vehicle used for track or train maintenance that has the ability to operate on the
rails. (Also spelled Hi-rail).
-
Home Signal
- A fixed signal at the entrance of a route or block to govern trains entering and using
that route or block.
-
HVAC
- Heating, Ventilation, and Air-Conditioning.
-
IANS (Integrated Alarm Notification System)
- Responsible for monitoring all components of the fire detection and suppression system;
the security status of station entrances, emergency exits, critical equipment rooms, and
TVMs. Monitors and controls emergency ventilation systems in tunnels,
monitors the status of elevators and escalators, and controls accessibility of elevators
and access to stations. IANS provides emergency telephones for passengers and fire
department personnel and public address to stations. On some systems, IANS has replaced
other systems integrated into SCADA.
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