Modeler's Terminology

The hobby of model railroading, like many hobbies, have a number of unique terms that are sometimes difficult to understand for people new to the hobby.  Below is a short listing of model railroad terms:

A

•  Accessory: a non-essential electric device.  Switch motors, signals, and block switches are just a few examples.
•  Air brush: a device which applies paint using compressed air.  Like a spray can, but with a steady supply of air and a much finer mist.
• Alternating Current:  Electricity that switches direction of travel, typically 60 times per second (60Hz) in the US. Used mostly in O scale, 3 rail trains.
• Amperage: a unit of measurement for the amount of electrical current.
•  Analog: Control of trains without digital signals.  Either through AC or DC electric current.

B

• Backdrop: a panel that is meant to give the illusion of distance on a mode railroad.  This can be a basic sky-blue board, painted scenes, photographs stitched together, among other methods.
• Ballast: gravel material meant to hold track in place.  For models, this material is finely crushed rock typically bought at hobby stores, although sifting real material is an option. 
• Benchwork: a structure which elevates the railroad above the floor.  This can be in the form of tables, shelf brackets, shelving, or custom designs. Kits are also available for the hobbyist without power tools for making their own.
• Block: a section of track that is electrically isolated.  May also refer to a section of track protected by signals, a form of prototypical railroad operations.
• Branchline: secondary lines which deviate from the mainline of the railroad. 

 C

• Cab: the part of the locomotive that the crew is stationed which has all the controls necessary to run the engine and hence the train. 
• Cab Control: an analog system of control where a DC or AC throttle is connected to an electrical block.
• Caboose: a piece of railroad equipment that was manned by the conductor and was used as a portable office as well as a place to store the train's paperwork.
• Clearance: space required for two pieces of railroad equipment to pass eachother and stationary objects. 
• Code: rail height, measured in thousandths of an inch.  Code 83 rail is 0.083 inches tall.
• Couplers: devices which allow railroad equipment to couple together to form a train.
• Crossover: a pair of turnouts that allows a train to move between multiple parallel tracks.  Found typically on mainlines and in yards. 
• Crossing: a place where two tracks running at angles to each other are able to pass each other safely.  Found at junctions and interchanges.

D

• Decoder: a small computer which receives DCC signals and converts them into physical commands.  Can be installed for stationary accessories, rolling stock, or locomotive control.
• Device: a part of an object which performs a physical function.
• Derailing: when railroad wheels are no longer running on the rails, but rather on the ground.
• Direct Current: electricity which flows in only one direction. Used in every scale.
• Digital Command Control: A control system that embeds direct current with alternating current signals in a binary format.
• Double Pole, Double Throw (DPDT): a switch which is used to alternate the polarity of a device.

E

• Easement (track): a section of track which eases a train into and out of a curve.
• Easement (surveying): land owned by the railroad and is measured from the track center.
• Engineer: the crewman who pilots the train.
• Era: Period of time that is modeled.
• Extra Train: a train which is not on a regular schedule.

F

• Finescale: a set of standards that have strict tolerances for scaled dimensions.
• Flex Track: model track sections of a long length (36 inches for HO scale) which are flexible enough to be bent into a curve.  Typically used in bulk for model railroads.
• Flying Junction: instead of a crossing, a flying junction allows two tracks to cross paths by elevating one track over the other.  This is found where tracks have an elevation difference due to terrain and in yards where ramps are built to allow track to rise and fall. 
• Fouling: The act of derailing or blocking a protected section of track.
• Frog: A part of a switch or crossover where two rails cross paths. The frog allows free travel for train wheels. on either path through the device.

G

• Gauge: width of railroad track measured between the inside faces of the rails.  Also the width of railroad wheels measured from the outside of the flange.
• Gap: a space made in a rail to electrically isolate a section of track.
• Ground Foam: scenery material meant to represent grass, bushes, and debris.
• Gradiant: a measurement of slope given as a percentage in North America and as a ratio elsewhere in the world.  A 2% grade has a rise of 2 feet for every 100 feet of travel, also displayed as 1/50.
• Ground Throw: a manual switch stand with no electrical controls, purely mechanical.
• Guard Rail: sections of track which prevent derailed axles from deviating from the track on turnouts and bridges.  Prevents a small derailment turning into a massive derailment.

H

• Highball: a signal which gives an approaching train to continue at speed into the next block.
• High Iron: slang for the mainline because such railroad tracks have heavy track demands, necessitating heavy duty rail.
• HO scale: Trains that are 1:87th the size of prototype equipment.
• Homosote: a brand of sound-deadening material which works well as track roadbed.

I

• Interchange: a small yard where trains at a junction can pickup and drop off cars.
• Interlocking signals: signals which are synchronized with turnouts so that the pathways are easily defined and protected for trains.

J

• Junction: a place where two railroads or a mainline and a branch line meet.
• Joiner: a piece which allows two rails to connect.

K

• Kadee: a popular manufacturer of couplers for N, HO, S, O, and G scale trains.  Used by many modelers for their reliability and uniform standards.

L

• Ladder: a series of switches which form multiple tracks for a yard.
• Large Scale: Also known as "G" scale trains.  The actual scale varies from 1:32nd to 1:13.7th the size of a prototype.  The variation is scale is used to represent different prototype gauges on 45mm track.  1:32nd represents standard gauge trains, 1:13.7th scale represents two foot gauge trains.  
• Layout: a model railroad.
• Lead Track: a track dedicated exclusively for switching engines to perform yard operations without interfering with the mainline.
• Light running: a moving train with no cars, at most a locomotive and caboose.
• Local: a train which serves small towns on a branchline or mainline.
• Lunar: signal color which is light blue on color, indicating either a stop or proceeding at restricted speed into the next block.

M

• Mainline: track which serves as the main artery for railroad operations.
• Mallet: a type of articulated locomotive that has two sets of driving wheels which allows travel on tighter curves.
• Manifest Freight: An express freight train with priority on railroad trackage.
• Meter: an electrical device which can read volts, amps, and resistance as well as other electrical aspects.
• Multiple Aspect Signaling: a signaling system that uses multiple colored lenses to communicate commands to the engineer.
• Multiple Unit: a way to connect two or more diesel locomotives together for more pulling power.

N

• Narrow Gauge: trains which operate on tracks with less than a 4' 8.5" width.
• N Scale: a model train scale that is 1:160th the size of the prototype.
• NMRA: National Model Railroad Association.  The largest model railroad organization in the world with a governing body that publishes standards.  Divisions of the NMRA organize events and oversee model competitions.
• Non-Revenue: equipment which is not used to make money for the railroad.
• Notch 8: A diesel locomotive running at full power.

O

• O Scale: a model train scale that is 1:48th the size of the prototype.
• Open Frame bench work: a system of layout bench work that does not require a solid top to build scenery and lay track.

P

• Point Rails: rails on a turnout which can be moved to alter the path of an oncoming train.
• Position Light Signal: a signal that uses the position AND color of lights to communicate commands.
• Pound: Standard measurement rail weight.  Represents the number of pounds one yard (3 feet) of rail.
• Prototype: objects found in the real world that are recreated in miniature.

Q

•  Queenpost: a device which supports the tension rod on a steam-era freight car.

R

• Radio Control: controlling trains wirelessly by using radio frequencies.
• Rail: Iron that is cast in an "I"shape that allows train wheels to freely roll.
• Railroad: A company that transports freight and passengers by rail.
• Ready-to-Run: model train equipment which can be used without assembly.
• Rerailer: a special piece of track that automatically fits wheels properly on the rails
• Roadbed: material that supports model railroad track.
• Ruling Gradient: the overall rise on a railroad division, which determines track speeds and power requirements.

S

• S Scale: a model train scale that is 1:64th the size of the prototype.
• Semaphore: a type of signal that uses a wooden or metal arm that is adjusted to different positions. Usually equipped with a matching set of lights for night operations.
• Single Pole, Single Throw: the most basic on-off electrical switch.
• Single Pole, Double Throw: an electrical switch with a center off position.
• Scale: a ratio between the size of the model and the size of the prototype.
• Scratchbuild: the practice of building a model from raw materials
• Sectional track: model railroad track that is made up of short, standardized sections that are meant to easily be put together and taken apart.
• Siding: a spare track where trains can pass eachother or for storing cars and equipment.
• Signal: a device which communicates commands to train crews visually.
• Staging: tracks arranged in a yard on a model railroad that represent the rest of the rail network not modeled on the layout.
• Switch: a turnout on a model railroad.  Also an electrical device that routes current to different circuits.
• Switchback: a track arrangement where a train pulls through a switch onto a tail track and then backs into the other leg of the switch.  Used in mountainous terrain or where there's no space to make a turn-back loop.
• Switch stand: a device which moves the point rails on a turnout.
• Switch machine: a mechanical device that throws a model railroad turnout electrically.

T

• Table-top: benchwork that uses a solid top as a base for track and scenery.
• Throttle: a control used by model railroaders to operate trains.  This can be an analog throttle, DCC throttle, or an R/C throttle.  Throttles can either be mounted directly on the layout, plugged into the railroad with a jack, or used wirelessly.  Smartphones can also be throttles with the right app.
• Traction: electrically operated streetcars and trams, either in an urban or interurban setting.
• Train Set: a product offered by manufacturers which includes a locomotive, a few railcars, a loop of track, and a throttle.  Accessories, multiple locomotives, and even DCC systems are sometimes included. Great way to be introduced to the hobby.
• Trolley: a small passenger unit that was pulled by horses in the early years, but was later powered by electricity or internal combustion engines.
• Turn-back loop: a track arrangement where the train reverses direction via a loop of track. Used in close quarters or in mountainous terrain.
• Turnout: a railroad switch that allows a train to travel on the current path or a diverging path.
• Turntable: a large device that allows locomotives and special equipment such as snow plows to be turned to face the opposite direction on the track.  Also used in conjunction with a roundhouse instead of using a switch ladder.

U

• Unit Train: a train that is made up of one type of freight, treated as one unit and is thus never taken apart or reorganized until reaching the destination. Reduces paperwork for the railroad.

V

• Volt: a unit of measurement for the "pressure" of electrical current.

W

• Watt: a unit of measurement for the power of electrical current.  Volts x Amps = Watts.
• Way Car: an alternate name for a railroad caboose.  The term is most common in the Midwest. 
• Whyte Notation: a method of classifying steam locomotives by the number of pilot wheels, driving wheels, and trailing wheels on the locomotive body.  Geared locomotives are not classified this was since all wheels are driving wheels.
• Wye: a track arrangement that allows an engine to turn directions.  The track is in a "Y" shape.

Y

• Yard: a series of parallel tracks used for storage and sorting of railroad equipment.

Z

• Z Scale: a model train scale that is 1:220th the size of the prototype.