Railroading Glossary
The following glossary is arranged alphabetically with each term catalogued by first letter. Select a letter below to begin.
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
Multiple unit. Electrical and pneumatic connections between locomotives that allow the operation of more than one unit from a single cab. Electric cars, operated in multiple and controlled by one person in the lead car, are also sometimes referred to as EMUs.
MacArthur engine
Redesignated name for Mikado-type (2-8-2) steam locomotives in honor of General Douglas MacArthur. Used by a handful of railroads during World War II.
Main line, or Main track
The principal running track of a railroad, as contrasted with sidings, spurs, and yard tracks.
Maintenance of way
The repair and maintaining of tracks, ballast, and related structures.
A type of articulated compound steam locomotive with two sets of cylinders, rods, and drive wheels under one boiler. The non-swiveling rear engine works at boiler pressure, and the swiveling front engine uses exhaust steam from the rear engine. Developed by Swiss inventor Anatole Mallet (mal-LAY, but often pronounced MAL-ley in the U.S.), this type of locomotive was substantially bigger than its predecessors, and was popular between roughly 1905-1925.
Paperwork describing the contents of a car or detailing a single shipment. Also, a freight train carrying goods not hauled in unit trains or intermodal trains.
Manual block
Train-control system in which the use of each section of track, called a block, is governed by signals that are either controlled manually or by block-limit signals, or both, upon receipt of information by phone or other means of communication.
Mark off
Report oneself as unavailable for work
Term for end-of-train (EOT) device, the modern end-of-train marker, placed on the rear coupler of a train to monitor air-brake system integrity and air pressure. Another acronym used to refer to these types of markers is FRED (Flashing Rear-End Device).
Mars light
Trademark name of an auxiliary headlight (there were several versions) whose beam revolved in a figure 8.
A slug built by General Electric for Seaboard Coast Line. The name is an acronym: Motors to Assist Tractive Effort.
When two trains approach from opposite directions and pass, one using a siding.
Absorption by a corporation of one or more others; or the issuing of additional securities by a major company in payment for the securities of a minor company whose corporate existence is then ended. In precise terms, Northern Pacific, Great Northern, and Burlington were not merged to form Burlington Northern but were merged by Burlington Northern. Sometimes a new name is involved: Seaboard Air Line merged Atlantic Coast Line and simultaneously adopted a new name, Seaboard Coast Line.
Originally a high-speed electric passenger car developed by the Pennsylvania Railroad and the U.S. Department of Transportation to improve service between New York and Washington. After the original passenger cars were downgraded, Amtrak continued to use the Metroliner name to market its high-speed Northeast Corridor passenger using other types of equipment. With the extension of electrified train service from New Haven to Boston, and the introduction of new higher-speed Acela trainsets in the year 2000, Amtrak retired the Metroliner brand name.
Microprocessor control
Miniaturized computers on board the locomotive monitoring and directing the prime mover and the electrical apparatus.
Nickname for a Mikado (2-8-2) steam locomotive.
Mixed train
A train carrying both freight and passengers, the latter either in passenger cars or in the caboose.
Montreal Locomotive Works, or successor MLW Industries.
Model board
Schematic diagram of an interlocking showing layout and status of tracks, switches, and signals.
Modular electronics
Any "black box" system whereby the electrical control apparatus of the locomotive is subdivided into plug-in components that can be replaced without disturbing other components.
Style of locomotive construction in which the sides and top of the carbody, not just the frame or platform, serve a structural function.
An electric locomotive (sometimes used for diesels in areas where electrics are common).
Motor car
Self-propelled passenger-carrying rail car built in the early 1900's. They were powered by gasoline engines (later diesel engines), which turned an electric generator which fed current to traction motors geared to the wheels. Most were built in the 1910's and 1920's; the last ones were removed from service around 1960. Also called "doodlebugs" and "puddle jumpers".
Movable-point frog
An advanced component in a track switch that provides continuous support for wheels as they cross the other rail, eliminating the gap that occurs in standard frogs where wheel flanges of cars taking one route "pass through" the railhead of the other. Also permits high-speed movement (70 mph or more) through switches.
A flatcar equipped with decks, walls, roof and end doors for transporting automobiles and light trucks on two or three levels. Also referred to as an auto rack.
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