Railroading Terms & Definitions

Western Rail Archive Reference Guide

Railroading has developed its own technical language over nearly two centuries of operation. This glossary explains frequently used railroad terminology in straightforward language for newcomers while preserving the distinctions valued by experienced readers.

Definitions can vary by railroad, country, historical period, and operating context. California examples are illustrative rather than exhaustive.

Glossary Organization

The glossary is grouped by subject so readers can browse related concepts together.

Service Types
Equipment Types
Infrastructure & Facilities
Operations, Personnel & Train Handling
Locomotive & Electrical Systems
Railroad Classification & Business
Industry, Railfan & Historical Terms

Service Types

These terms describe the principal purpose or operating form of a railroad or transit service.

Passenger Rail

Rail transportation intended primarily to carry passengers rather than freight. Passenger rail includes intercity, commuter, regional, rapid-transit, light-rail, streetcar, excursion, and other services.

California Examples Include:

See also: Freight Rail, Intercity Rail, Commuter Rail

Freight Rail

Rail transportation intended primarily to move goods, commodities, containers, trailers, and industrial products.

California Examples Include:

BNSF Railway
Union Pacific Railroad
San Joaquin Valley Railroad

See also: Intermodal, Piggyback, Class I Railroad

Mail & Express Rail

Rail transportation used to carry mail, parcels, express shipments, and other time-sensitive cargo. Historically, many passenger trains included Railway Post Office cars and express equipment. Dedicated railroad mail service has largely disappeared, but it was an important part of passenger-train economics.

California Examples Include:

Santa Fe mail and express trains
Southern Pacific mail and express trains
Amtrak mail and express operations (historically)

See also: Passenger Rail, Freight Rail

Intercity Rail

Passenger rail service primarily intended to connect cities rather than provide local urban transportation. Intercity trains generally operate over longer distances and make fewer stops than commuter or rapid-transit services.

California Examples Include:

Amtrak Pacific Surfliner
Gold Runner (formerly Amtrak San Joaquins)
Amtrak Coast Starlight

See also: High-Speed Rail, Commuter Rail, Regional Rail

High-Speed Rail

Passenger rail service designed to operate at substantially higher speeds than conventional rail service, usually with purpose-built equipment, advanced signaling, and significant stretches of dedicated infrastructure. Definitions vary, but dedicated high-speed lines are commonly associated with operation at or above 125 mph (200 km/h).

California Examples Include:

California High-Speed Rail (under construction)
Brightline West (planned and under development)

Railfan Note: High-speed rail is usually defined by both speed and infrastructure. A fast train operating briefly at high speed over a conventional railroad is not necessarily a complete high-speed rail system.

Commuter Rail

Passenger rail service traditionally designed to connect outlying communities with central employment districts. Modern commuter rail may operate throughout the day and serve many trip purposes beyond the traditional rush-hour commute.

California Examples Include:

Metrolink
COASTER
Caltrain

Regional Rail

Passenger rail service connecting communities within a metropolitan area or broader region, often offering all-day service for commuting and non-commute trips. The boundary between regional and commuter rail varies by agency and country.

California Examples Include:

Metrolink Arrow
NCTD SPRINTER
Sonoma-Marin Area Rail Transit (SMART)

Rapid Transit

High-capacity urban passenger rail operating on an exclusive or fully separated right-of-way, generally with frequent service and closely spaced stations.

California Examples Include:

BART
Los Angeles Metro B Line
Los Angeles Metro D Line

Light Rail

Electrically powered urban or regional rail that can operate in streets, dedicated rights-of-way, medians, subways, or elevated structures. Light rail generally uses smaller and more flexible equipment than conventional mainline railroads.

California Examples Include:

San Diego Trolley
Los Angeles Metro A, C, E, and K Lines
San Francisco Muni Metro

Streetcar

Urban rail service operating primarily in or alongside city streets, commonly with frequent stops and shorter vehicles than conventional railroad equipment. Modern streetcars and light rail overlap, but streetcars are usually more closely integrated with street traffic.

California Examples Include:

San Francisco F Market & Wharves
San Francisco Muni heritage streetcars

See also: Trolley, Light Rail, Cable Car

Interurban

An electric railway connecting cities and towns, often combining street running with private right-of-way and railroad-like operation.

California Examples Include:

Pacific Electric Railway
Sacramento Northern Railway
Key System

Railfan Note: Many interurbans blurred the line between railroad and streetcar. A single trip could operate through city streets, cross open country, and enter another downtown without requiring passengers to transfer.

See also: Streetcar, Light Rail, Passenger Rail

Equipment Types

These terms describe locomotives, passenger equipment, and self-propelled rail vehicles.

Locomotive

A powered railroad vehicle designed primarily to move trains. A locomotive normally contains propulsion and control equipment but generally does not carry revenue passengers or freight.

See also: Motive Power, Rolling Stock

Steam Locomotive

A locomotive that burns fuel to heat water in a boiler, producing steam that drives pistons connected to the driving wheels. Steam locomotives dominated railroading before diesel and electric power became widespread.

California Examples Include:

Santa Fe 3751
Southern Pacific 4449
Union Pacific 4014

See also: Locomotive, Prime Mover

Diesel-Electric Locomotive

A locomotive in which a diesel engine drives a generator or alternator. The electrical power produced operates traction motors connected to the wheels; the diesel engine does not normally drive the wheels directly.

Electric Locomotive

A locomotive powered by electricity collected from an overhead wire or third rail rather than produced by an onboard diesel engine. Electric locomotives usually collect current through a pantograph or contact shoe.

A Unit

A locomotive equipped with an operating cab. The term is most closely associated with streamlined diesel locomotives that operated in matched sets of cab-equipped A units and cabless B units.

California Examples Include:

Santa Fe F7A locomotives
Southern Pacific E9A locomotives
Union Pacific E8A locomotives

Railfan Note: Classic locomotives often operated in A-B-B-A formations. The A units contained the operating cabs, while the B units supplied additional power.

See also: B Unit, Multiple Unit (MU), F Unit

B Unit

A locomotive built without a conventional operating cab and normally controlled from an attached A unit through multiple-unit connections.

California Examples Include:

Santa Fe F7B locomotives
Southern Pacific F7B locomotives
Union Pacific E9B locomotives

Railfan Note: B units were common during dieselization but became less common as railroads favored the operating flexibility of cab-equipped locomotives.

See also: A Unit, Multiple Unit (MU), F Unit

Diesel Multiple Unit (DMU)

A self-propelled passenger rail vehicle with onboard diesel propulsion. DMUs can operate individually or in connected sets and do not require a separate locomotive.

California Examples Include:

NCTD SPRINTER (Siemens Desiro VT642)
Metrolink Arrow (Stadler FLIRT DMU)
Sonoma-Marin Area Rail Transit (SMART)

Electric Multiple Unit (EMU)

A self-propelled passenger rail vehicle that draws power from an overhead wire or third rail. Multiple cars can be connected and controlled as one train without a separate locomotive.

California Examples Include:

Caltrain electric fleet
BART
Los Angeles Metro B and D Lines

Railfan Note: Most modern light-rail vehicles satisfy the literal engineering concept of an EMU, but North American usage more often applies the term EMU to commuter, regional, and rapid-transit equipment.

Cab Car

A passenger car equipped with an operating cab from which an engineer can control a train. A locomotive at the opposite end can push the train while being controlled from the cab car.

Non-Powered Control Unit (NPCU)

A locomotive or locomotive-derived vehicle that no longer supplies traction power but retains an operating cab from which a compatible train can be controlled.

Railfan Note: An NPCU permits push-pull operation without moving the powered locomotive to the other end of the train. COASTER 2105 can serve this role when connected to a compatible powered locomotive.

See also: Cab Car, Cabbage, Multiple Unit (MU)

Heavyweight Passenger Equipment

Passenger cars built primarily during the late nineteenth and early twentieth centuries using heavy steel construction and traditional railroad design practices. Heavyweights commonly featured riveted bodies, substantial underframes, and clerestory roofs.

California Examples Include:

Southern Pacific heavyweight passenger cars
Santa Fe heavyweight passenger cars
Union Pacific heavyweight passenger cars

Railfan Note: Many museum passenger cars are heavyweights because their robust construction helped them survive long after retirement from first-class service.

Lightweight Passenger Equipment (Streamliner)

Passenger equipment developed beginning in the 1930s using lighter construction, improved aerodynamics, and modern styling. Stainless steel, aluminum, and welded steel construction reduced weight and became closely associated with the streamliner era.

California Examples Include:

Santa Fe Super Chief equipment
Southern Pacific Daylight equipment
Amtrak Superliner fleet

Railfan Note: Railfans often call an entire train a streamliner, but the term is closely associated with the lightweight, streamlined equipment that gave those trains their distinctive appearance.

Bi-Level Car

A passenger car containing seating or passenger space on two levels. Bi-level equipment increases capacity without requiring a proportionally longer train.

See also: Loading Gauge, Passenger Rail

Railcar

A broad term for a railroad vehicle. Depending on context, it may mean a freight or passenger car, or a self-propelled passenger vehicle. The intended meaning should be made clear in surrounding text.

Trainset

A group of passenger cars or self-propelled vehicles intended to operate together. Some trainsets can be rearranged, while others are semi-permanently coupled.

Yard Switcher

A locomotive designed primarily for low-speed switching in yards, terminals, ports, and industrial facilities rather than long-distance road service. Switchers emphasize visibility, tractive effort, and frequent changes of direction.

California Examples Include:

EMD SW1500
EMD MP15DC
Pacific Harbor Line switching locomotives

See also: Yard, Switching, Road Switcher

Infrastructure & Facilities

These terms describe tracks, junctions, railroad property, operating locations, and railroad buildings.

Main Line

A railroad’s principal through route or one of its primary routes, normally used for movements between major terminals, junctions, cities, ports, or industrial regions.

See also: Branch Line, Siding, Double Track

Branch Line

A secondary route extending from a main line to serve a community, industry, agricultural district, port, or other destination.

See also: Main Line, Spur

Spur

A track branching from another track to serve an industry, loading facility, storage location, or customer. A spur usually ends rather than reconnecting at both ends.

See also: Siding, Branch Line

Siding

A secondary track connected to a main track, usually at both ends, that allows trains to meet, pass, wait, or clear the main line.

Railfan Note: A siding is not the same as a double-track main line. On double track, both tracks are main tracks. A train entering a siding leaves the main track for a secondary track.

See also: Main Line, Double Track, Spur

Yard

A group of tracks used to sort, assemble, inspect, store, service, or repair trains and railroad equipment. Yards range from small local facilities to large classification complexes.

California Examples Include:

San Bernardino Yard
Hobart Yard
Roseville Yard

Railfan Note: A large classification yard can function like a railroad city, with dispatchers, yardmasters, switch crews, mechanical employees, fueling facilities, and maintenance forces working around the clock.

See also: Hump Yard, Switching, Yard Switcher

Hump Yard

A classification yard that uses a raised track, or hump, to sort freight cars. Cars are pushed over the hump and roll by gravity into designated classification tracks.

California Examples Include:

West Colton Yard
Barstow Yard
Roseville Yard

Railfan Note: Computer-controlled retarders can regulate the speed of cars rolling into classification tracks, making gravity sorting a distinctive railroad operation.

See also: Yard, Switching

Right-of-Way

The land occupied or controlled by a railroad for tracks and associated infrastructure. Railroad right-of-way is generally private property and should not be entered without authorization.

See also: Main Line, Trackage Rights

Block

A defined section of track used to control train movements and maintain safe separation. Signals or operating authorities indicate whether a train may enter a block.

Control Point

A designated location where signals, switches, or routes are controlled to govern train movements.

See also: Interlocking, Dispatcher, Block

Interlocking

An arrangement of signals and switches designed so that conflicting train movements cannot be authorized at the same time.

See also: Control Point, Diamond, Flyover

Diamond

An at-grade crossing where two railroad tracks intersect. Special railwork and flangeways allow wheels to cross in either direction.

California Examples Include:

Colton Crossing before construction of the flyover
Crossings within terminal districts
Industrial railroad crossings

Railfan Note: A diamond can create a distinctive series of impacts as wheels cross it. A flyover removes the conflict by carrying one route above the other.

See also: Flyover, Interlocking

Double Track

A railroad route containing two main tracks. Each may normally favor one direction, although modern signaling can permit trains to operate in either direction on either track.

See also: Main Line, Siding

Track Gauge

The distance between the inside faces of the two rails. Standard gauge measures 4 feet 8 1/2 inches (1,435 mm); broad gauge is wider and narrow gauge is smaller.

California Examples Include:

Amtrak (standard gauge)
BART (broad gauge)
Disneyland Railroad (narrow gauge)

Railfan Note: Most North American railroads use standard gauge. BART uses 5 feet 6 inches (1,676 mm), while the Disneyland Railroad uses 3 feet (914 mm), similar to many historic narrow-gauge railroads of the American West.

See also: Loading Gauge, Main Line

Loading Gauge

The maximum height and width of railroad equipment that can safely operate over a route. Tunnels, bridges, platforms, overhead wires, signals, and other structures determine the available clearance.

California Examples Include:

BNSF Transcon routes accommodating double-stack trains
Union Pacific Sunset Route
Amtrak routes accommodating Superliner equipment

Railfan Note: Track gauge and loading gauge are different. Track gauge measures the distance between the rails; loading gauge determines how large the vehicle can be. Amtrak Superliners are common in the West but cannot operate on most Northeast Corridor services, principally because of restrictive clearances such as the Hudson River tunnels between New Jersey and New York.

See also: Track Gauge, Intermodal, Bi-Level Car

Grade

The slope of a railroad track, generally expressed as a percentage. A 1 percent grade rises or falls approximately one foot for every 100 feet of horizontal distance.

See also: Main Line, Tractive Effort

Grade Crossing

A location where a road or pedestrian path crosses railroad tracks at the same level. Also called a level crossing in many countries.

See also: Flyover, Grade

Flyover

A grade-separated railroad crossing where one track passes over another on a bridge or elevated structure, eliminating conflicting at-grade movements.

California Examples Include:

Redondo Junction Flyover
San Bernardino Yard Flyover
Colton Crossing Flyover

Railfan Note: Southern California’s heavy freight and passenger traffic has made flyovers valuable for removing conflicts and improving capacity.

See also: Diamond, Interlocking, Control Point

Trackage Rights

An agreement allowing one railroad to operate its trains over tracks owned by another railroad.

See also: Right-of-Way, Interchange

Wye

A triangular arrangement of tracks used to turn locomotives, cars, or entire trains. A movement reverses through part of the triangle and emerges facing the opposite direction.

See also: Turntable, Switching

Turntable

A rotating bridge used to move locomotives or cars between tracks or turn equipment to face the opposite direction. Turntables were commonly paired with roundhouses.

See also: Roundhouse, Wye

Roundhouse

A curved or circular locomotive-maintenance building arranged around a turntable. Individual stalls allow locomotives to enter for inspection, servicing, or repairs.

See also: Turntable, Yard

Passenger Station

A facility where passenger trains stop to board and discharge passengers. Stations may include platforms, waiting rooms, ticketing, baggage facilities, transit connections, and historic depot buildings.

See also: Passenger Rail, Freight Depot

Freight Depot

A railroad building or facility used to receive, store, and transfer less-than-carload freight, express shipments, or other goods between trains and local customers.

See also: Freight Rail, Passenger Station, Intermodal

Operations, Personnel & Train Handling

These terms describe railroad jobs and the ways trains are controlled, assembled, and moved.

Dispatcher

A qualified railroad employee who controls or coordinates train movements over an assigned territory. Dispatchers may operate signals and switches, issue movement authorities, coordinate maintenance access, and communicate with train crews.

Railfan Note: Dispatchers are often compared with air-traffic controllers, but they work within railroad-specific rules, signal systems, territories, and movement-authority procedures.

Conductor

The train-crew member responsible for the train, its consist, required documentation, rule compliance, and coordination of the crew’s work. Duties vary between freight, passenger, excursion, and museum operations.

Railfan Note: The closest railroad parallel to the captain of a ship is the conductor. The engineer operates the locomotive, while the conductor is generally responsible for the train itself and coordinates the crew.

See also: Engineer, Brakeman, Dispatcher

Engineer

The qualified crew member who operates a locomotive or other powered railroad equipment. The engineer controls speed, acceleration, braking, and train handling while complying with signals, authorities, rules, and restrictions.

Railfan Note: In North American railroad terminology, an engineer operates the locomotive. Some transit systems instead use the title operator or driver, particularly on light-rail, rapid-transit, and streetcar systems.

See also: Conductor, Dispatcher

Brakeman

Historically, a train-crew member responsible for hand brakes, coupling and uncoupling cars, throwing switches, protecting movements, inspecting equipment, and assisting the conductor.

Railfan Note: In the era of hand brakes, brakemen sometimes moved across the tops of freight cars to apply individual hand brakes. Front and rear brakemen were once common, and the work was physically demanding and dangerous.

See also: Conductor, Air Brake, Switching

Consist

The locomotives and cars assembled to form a train. The term may also refer specifically to a group of locomotives connected and operated together.

See also: Trainset, Multiple Unit (MU)

Multiple Unit (MU)

A control system allowing several connected locomotives to respond to commands from one operating cab. MU connections can transmit throttle, direction, braking, and other control commands.

Push-Pull Operation

A method of passenger-train operation in which a locomotive pulls in one direction and pushes in the other. A cab car or NPCU allows the crew to operate from the end opposite the locomotive.

Positive Train Control (PTC)

A safety system designed to prevent specified accidents, including certain train-to-train collisions, overspeed derailments, unauthorized incursions into work zones, and movements through improperly aligned switches. The system monitors train movement and can intervene when required.

California Examples Include:

Amtrak Pacific Surfliner
Metrolink
COASTER

See also: Dispatcher, Block, Control Point

Distributed Power

Locomotives placed in the middle or at the rear of a train and remotely controlled from the lead locomotive. Distributed power can improve train handling and reduce forces in long or heavy trains.

See also: Multiple Unit (MU), Consist

Light Engine

One or more locomotives moving without railroad cars.

See also: Deadhead Move, Locomotive

Foreign Power

A locomotive operating on a railroad other than the one that owns it.

See also: Interchange, Motive Power

Interchange

The transfer of railroad cars, locomotives, or traffic between different railroad companies, allowing freight and equipment to travel beyond one railroad’s network.

See also: Trackage Rights, Foreign Power

Switching

The process of moving, sorting, assembling, or separating railroad cars. Switching occurs in yards, at industries, terminals, and while preparing trains.

See also: Yard, Yard Switcher, Consist

Locomotive & Electrical Systems

These terms describe locomotive propulsion, electrical collection, braking, and train-power systems.

Prime Mover

The principal engine that produces power aboard a diesel locomotive. In a diesel-electric locomotive, the prime mover drives a generator or alternator that supplies electricity to the traction motors.

Head-End Power (HEP)

Electricity supplied by a locomotive, generator car, or other source for passenger-car lighting, heating, air conditioning, outlets, and onboard systems.

Railfan Note: The prime mover and HEP generator on COASTER 2105 were disabled as part of its preservation arrangement.

See also: Passenger Rail, Prime Mover

Traction Motor

An electric motor that turns the wheels of a diesel-electric or electric locomotive or self-propelled rail vehicle.

See also: AC Traction Motor, DC Traction Motor

AC Traction Motor

A traction motor powered by alternating current. AC traction generally provides strong adhesion, reduced maintenance, and effective low-speed pulling performance.

California Examples Include:

BNSF ES44C4 locomotives
BNSF ET44C4 locomotives
Union Pacific ES44AC locomotives

Railfan Note: On many CSX Transportation locomotives, lightning-bolt decals identify units equipped with AC traction motors rather than DC traction motors.

See also: DC Traction Motor, GEVO, Traction Motor

DC Traction Motor

A traction motor powered by direct current. DC traction dominated North American diesel-locomotive construction for much of the twentieth century and remains in widespread service.

California Examples Include:

Santa Fe SD45-2 No. 5704
Southern Pacific SD40T-2 locomotives
BNSF Dash 9 locomotives

See also: AC Traction Motor, Traction Motor

Dynamic Brake

A braking system in which traction motors act as generators to help slow a locomotive or train. On most diesel-electric locomotives, the generated electricity is converted to heat and released through resistor grids.

See also: Traction Motor, Air Brake

Tractive Effort

The pulling or pushing force produced by a locomotive, usually expressed in pounds or kilonewtons. Tractive effort is especially important when starting or moving heavy trains at low speed.

See also: Horsepower, Grade

Horsepower

A measurement of power commonly used to describe locomotive output. Horsepower alone does not determine pulling capacity; adhesion, gearing, tractive effort, speed, train weight, and track conditions also matter.

See also: Tractive Effort, Prime Mover

Air Brake

A braking system using compressed air to apply and release brakes throughout a train, allowing the engineer to control locomotive and car brakes from the operating cab.

See also: Dynamic Brake, Brakeman

Pantograph

A roof-mounted device that collects electrical power from an overhead wire. Pantographs are used on electric locomotives, EMUs, high-speed trains, and many light-rail vehicles.

California Examples Include:

Caltrain electric fleet
Los Angeles Metro light-rail vehicles
Future California High-Speed Rail trainsets

Railfan Note: Pantographs maintain reliable contact at higher speeds and have largely replaced trolley poles on modern electric railways.

See also: Trolley Pole, Electric Locomotive

Trolley Pole

A spring-loaded pole mounted on a streetcar or electric railway vehicle that collects electricity from an overhead wire through a wheel or sliding shoe.

California Examples Include:

Historic San Francisco streetcars
Pacific Electric equipment (historically)
Sacramento Northern equipment (historically)

Railfan Note: The word trolley originally referred to the current-collecting wheel at the end of the pole, not the entire streetcar. The name later expanded to the vehicle and sometimes the whole system.

See also: Pantograph, Trolley, Streetcar

Railroad Classification & Business

These terms describe regulatory classifications, revenue-producing activity, equipment positioning, and freight business.

Class I Railroad

A railroad in the largest annual operating-revenue category established by the Surface Transportation Board. Thresholds are adjusted for inflation.

California Examples Include:

BNSF Railway
Union Pacific Railroad

Railfan Note: Class I is a financial and regulatory classification. It does not describe service quality, train speed, or the physical condition of a railroad.

See also: Class II Railroad, Class III Railroad

Class II Railroad

A railroad whose annual operating revenue falls below the Class I threshold but above the Class III threshold established by the Surface Transportation Board. Class II railroads are often called regional railroads, although industry and regulatory definitions do not always align exactly.

Railfan Note: A railroad’s class can change as its revenue changes; the classification does not necessarily indicate the physical size of its network.

See also: Class I Railroad, Class III Railroad

Class III Railroad

A railroad whose annual operating revenue falls below the Class II threshold established by the Surface Transportation Board. This category commonly includes short lines and switching or terminal railroads.

California Examples Include:

San Joaquin Valley Railroad
Pacific Harbor Line
Sierra Northern Railway

Railfan Note: A railroad can be small by revenue or mileage and still be important, providing the final connection between local customers and the national network.

See also: Class I Railroad, Class II Railroad

Revenue Service

Operation in which railroad equipment is performing its intended transportation role for paying passengers or revenue-producing freight. Operational equipment may also move in tests, training, museum demonstrations, or positioning moves outside revenue service.

Railfan Note: A scheduled COASTER train carrying passengers is in revenue service. The same equipment moving empty to a yard is not.

See also: Deadhead Move, Passenger Rail, Freight Rail

Deadhead Move

The movement of railroad equipment or employees without carrying revenue passengers or freight. Passenger equipment may deadhead between a yard, station, maintenance facility, or another assignment.

Railfan Note: A deadhead train can resemble a normal passenger train even though it is closed to passengers. The term can also describe an employee traveling without performing the regular operating assignment.

See also: Revenue Service, Yard

Intermodal

The movement of freight using two or more transportation modes, such as railroad, truck, and ship, without unloading the contents of the container or trailer during each transfer.

California Examples Include:

Port of Los Angeles
Port of Long Beach
BNSF and Union Pacific intermodal terminals

Railfan Note: Intermodal trains are often time-sensitive because rail service competes directly with long-distance trucking and connects with ship schedules.

See also: Piggyback, Freight Rail

Piggyback

A form of intermodal transportation in which highway trailers are carried directly on railroad flatcars. The formal abbreviation is TOFC, meaning Trailer-on-Flatcar.

Railfan Note: Piggyback and container service are related but different. A trailer retains its highway body and wheels, while a container is transferred between ships, trains, and truck chassis. Container-on-flatcar is abbreviated COFC.

See also: Intermodal, Freight Rail

Industry, Railfan & Historical Terms

These terms include railroad-industry language, locomotive families, informal nicknames, and historical concepts.

AAR

The Association of American Railroads, an industry organization representing major North American freight railroads. AAR standards and practices address equipment compatibility, interchange, reporting marks, mechanical requirements, and communications.

See also: Reporting Mark, Interchange

Reporting Mark

A unique series of letters assigned to identify the owner or operator of railroad equipment. Reporting marks are normally followed by a locomotive or car number.

See also: AAR, Rolling Stock

Rolling Stock

Railroad vehicles that move on the tracks, including passenger cars, freight cars, cabooses, and some self-propelled equipment. Context determines whether locomotives are included or discussed separately as motive power.

See also: Motive Power, Railcar

Motive Power

The locomotives or self-propelled equipment used to move trains.

See also: Locomotive, Rolling Stock

Heritage Unit

A modern locomotive painted in a scheme commemorating a predecessor railroad, historic locomotive, military organization, community, or event. A heritage unit remains active equipment rather than an original historic locomotive.

See also: Fallen Flag, Reporting Mark

Geep

An informal nickname for locomotives in EMD’s GP, or General Purpose, series.

Railfan Note: Railroaders and railfans began pronouncing the letters GP as “Geep,” and the nickname stuck.

GEVO

A railfan and industry nickname for locomotives powered by General Electric’s GEVO engine family and, more broadly, for many GE Evolution Series locomotives.

California Examples Include:

BNSF ES44DC locomotives
BNSF ET44C4 locomotives
Union Pacific ES44AC locomotives

Railfan Note: Railfans often call modern six-axle GE Evolution Series locomotives “GEVOs” while still distinguishing specific models such as ES44AC, ES44C4, and ET44C4.

F Unit

A family of streamlined diesel locomotives produced by General Motors’ Electro-Motive Division. F units became closely associated with dieselization and served in freight and passenger service.

See also: A Unit, B Unit, Covered Wagon

Tunnel Motor

A nickname most closely associated with Southern Pacific SD40T-2 and SD45T-2 locomotives designed with low-mounted radiator air intakes for operation in long tunnels and snow sheds.

Railfan Note: Southern Pacific sought cooler air nearer track level because hot exhaust accumulated near tunnel roofs and could contribute to overheating.

Wide Cab

A locomotive cab wider than the traditional narrow short hood, generally providing improved crew space, visibility, and collision protection. The term is often used informally for North American comfort-cab designs.

See also: Safety Cab, Road Switcher

Safety Cab

A locomotive cab designed with enhanced crashworthiness and crew protection compared with older conventional cabs. The term can overlap with wide cab or comfort cab, but the exact design and regulatory meaning vary.

See also: Wide Cab, Locomotive

Covered Wagon

A railfan nickname for streamlined cab-unit diesels, especially EMD E and F units, whose full-width carbodies concealed the machinery and running boards.

Railfan Note: The rounded, enclosed profile reminded enthusiasts of a covered wagon when viewed from the side.

See also: F Unit, A Unit, B Unit

Road Switcher

A locomotive designed to combine road-service performance with the visibility and accessibility needed for switching. Road switchers usually have narrow hoods and exterior walkways.

Railfan Note: The EMD GP7, introduced in 1949, helped popularize the road-switcher concept and replaced many specialized cab-unit and switching designs.

See also: Geep, Yard Switcher

Cabbage

An informal term combining cab and baggage. It refers to former F40PH locomotives converted into NPCUs with baggage space in the former machinery compartment.

Railfan Note: Not every NPCU is a cabbage. The nickname properly refers to the cab-and-baggage conversion associated with Amtrak’s rebuilt F40PH units.

Fallen Flag

A railroad identity that no longer operates under its former name because the company merged, was acquired, reorganized, or ceased operation.

California Examples Include:

Railfan Note: Fallen flags remain important to preservation. Equipment, depots, paint schemes, documents, and surviving rights-of-way can preserve an identity long after the corporation disappears.

See also: Heritage Unit, Reporting Mark

Heavy Rail

A context-dependent term. Transit agencies often use heavy rail for high-capacity rapid-transit systems on exclusive rights-of-way. In broader railroad discussion, it may distinguish conventional freight, intercity, and commuter railroads from light rail and streetcars.

California Examples Include:

BART (transit sense)
Metrolink (broader sense)
BNSF Railway (broader sense)

Railfan Note: Because transit professionals and railfans use the term differently, WRA articles should identify the intended meaning from context.

See also: Rapid Transit, Light Rail, Freight Rail

Trolley

A flexible and often informal term that can refer to a streetcar or light-rail vehicle, a trolley pole or wheel, or an entire transit system. The specific meaning depends on context.

California Examples Include:

San Diego Trolley
Historic San Francisco streetcars

See also: Trolley Pole, Streetcar, Light Rail

Cable Car

A rail vehicle pulled by a continuously moving cable beneath the street rather than by an onboard traction motor. A grip mechanism engages and releases the cable so the car can start, stop, and control speed.

California Examples Include:

Powell-Hyde Line
Powell-Mason Line
California Street Line

Railfan Note: Cable cars and streetcars are not the same. Streetcars carry their own propulsion equipment, while cable cars are pulled by an external moving cable.

See also: Streetcar, Trolley

Archive Status

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Foundational Article	Reference	Glossary	Not Applicable