General Locomotive and Equipment Terms

Below are many general locomotive and equipment terms that broadly cover both. Also, if you have any questions about the meanings of any of these definitions or simply have more to add that are not covered here please do not hesitate to get in touch with me.

Air test: Checking a train's air brakes to make sure that they are functioning correctly before beginning a journey.

All black: An "all clear" signal that means the train has no defects which would be noticeable against the black running gear.

Alco 251: The 251 engine replaced Alco's trouble-prone 244 model and was built between 1953 and 1969 (at which point locomotives were fairly reliable from then on), and today Montreal Locomotive Works and Bombardier continue to produce the engine. According to Trains.com, "the "2" indicates a 9-inch cylinder diameter and 10-inch stroke; '51' is for the year it was first tested."

APU: Stands for auxiliary power unit.

Angle cock: The valve found at the ends of locomotives and freight/passenger cars. These valves are almost always found in the open position on cars found within a train to allow the air to flow properly but closed at the end to keep proper air pressure maintained.

Anti-climber: This feature on a locomotive prevents obstructions that might be on the right-of-way in front of the locomotive from climbing up to the cab and possibly injuring the crew. They are found on either end of the locomotive.

ATC: Standing for Automatic Train Control, a feature in new locomotives which among other features, regulates the train's speed (for instance if the train exceeds a signal's speed limit the brakes are automatically applied).

ATS: Standing for Automatic Train Stop this technology (found either equipped to the locomotive or along the right-of-way) is required with speeds of 79 mph and above, it will automatically apply the brakes if the engineer does not recognize a restrictive signal within 20 seconds of passing it.

Blue flag: A blue-colored flag, sign, or light that is placed on a freight car indicating it is being worked on and cannot be moved.

Cab signal: Signal located in a locomotive or operating cab that indicates the conditions affecting train movement. Can be used in conjunction with, or in place of, lineside block signals.

Coupler: Technically known as a knuckle-coupler, the knuckle is the component that actually locks with an opposed-facing knuckle to fasten cars and locomotives together.

Engine: A term sometimes used to describe railroad locomotives whether it be powered by steam, diesel-electric, or electric.

EOT device: Stands for end-of-train device it is also known a FRED (Flashing Rear End Devices) and monitors a train's air brakes from the rear car (it also contains a flashing red light for safety purposes). The device replaced the fabled caboose in the 1980s.

Equipment trust: Based on the same principal of purchasing a car via a loan this is the way for railroads to purchase new locomotives and rolling stock via payments. The financial institution that provides the capital actually owns the equipment until the railroad has repaid its debt.

Export model: A locomotive designed and built for railroads outside of the United States and North America.

Flange: Usually about one inch deep it is the small lip found on the inside of rail wheels and guides/keeps the locomotive or car on the track.

Flange oiler: Components usually built into locomotives that automatically lubricate the flange to prevent wear (sometimes also found along right-of-ways).

Flangeway: The groove found between railroad tracks that allows the flange to pass unimpeded (usually at a crossing or other pave area).

Flat spot: The result of an axle locking up and sliding for a significant distance which causes that area in contact with the rail to wear away. One can tell when an axle has a flat spot by the loud, constant, banging noises given off by the freight car.

Flat switching: Switching freight cars in a yard that has no hump capabilities and locomotives must constantly move the cars around themselves.

Flexicoil truck: According to Trains.com "Electro-Motive Division's term for the truck that is standard on its six-axle units and available as an option on four-axle units. It is characterized by sets of coil springs between the bolster and the truck frame. The standard Type A switcher truck is a stiff, hard-riding truck; the four-wheel Flexicoil truck lets switchers ride better at road speeds."

Foreign: The term used by railroads to designate locomotives or cars that are owned by other railroads when operating on their property.

Goat: Slang for yard engines.

Grapevine throttle: According to Trains.com, "in a steam locomotive (such as UP 844), a throttle whose handle extends downward from the linkage overhead (vs. horizontally)."

Hand brake: Available on all locomotives and cars to manually apply or release brakes.

Helper: A locomotive added as extra power to a train to assist it over a steep grade.

High-adhesion truck: This type of truck, used specifically on locomotives, is meant to improve wheel-to-rail contact.

Horsepower hour: According to Trains.com, "when locomotives began to be leased on a performance-use basis rather than on time alone, a new measurement was devised, the horsepower hour, recorded by on-board microprocessors. For example, a 3900-horsepower LMX Dash 8-39B operating for an hour at full power runs up a charge of 3900 horsepower hours."

Independent brake: This valve allows an engineer to control the brakes on his/her lead locomotive (or group of locomotives), separate from the rest of the train.

Inline: According to Trains.com "arrangement of the cylinders of an engine in a single row; V-type engines have two rows of cylinders angled away from each other, all driving the same crankshaft."

Light engines: Locomotives operating by themselves pulling no cars or equipment of any kind.

Light-engine movements: Just a term to describe locomotives operating between locations without any cars.

Lightweight cars: Passenger cars built after the mid-1930's with streamlined exteriors and less overall weight than earlier equipment known as heavyweight cars.

LRV: Stands for light rail vehicle.

Piggyback: The term that often refers to truck trailers being hauled by train, also known as Trailers On Flatcar or TOFC service.

RCE: Stands for remote control equipment.

Rebuilding: Refers to breaking down a locomotive for refurbishment whereby new parts and components (sometimes upgraded, for instance, an SD40-2 will be rebuilt as an SD40-3) are used to replace those which are worn out. Doing this is usually much cheaper than buying a new locomotive outright.

Remote power unit: See slug.

RoadRailer: A term used to describe trailers, similar to traditional truck trailers, that have the ability to operate over highways as well as on rails.

Sperry car: Describes a car used by Sperry Rail Services to detect defects in the rail.

Steam generator: Mostly defunct today as electricity has replaced these steam generators, it was placed in diesel-electrics and electrics to provided heat (through the use of steam) for passengers.

Trackmobile: According to Trains.com, "a trademarked name by the Whiting Corp. for its car mover, a tractor equipped with rubber tires as well as flanged steel wheels, capable of hauling a few freight cars on a track or moving by itself off-rail. Essentially a cross between a tractor and a locomotive."

Yard goat: A term used to describe a switch engine.

Yaw dampers: A truck-mounted spring that helps to reduce extreme rocking of a locomotive or freight car in motion.

For more on general locomotive and equipment terms, like those above, please visit, and consider joining, the American Rails Forums, a family-friendly community where there are plenty of knowledgeable folks to help answer any questions you might have.

Also, if you are interested in knowing the meaning of a term that is not listed above please do not hesitate to contact me and if I do now know the answer myself I will hunt around or ask until I do! One way or another you will eventually get an answer.