Trucking Terms


‘A’ train

An ‘A’ train is a tractor pulling a semi trailer with a shorter trailer or pup by means of reach or spindle hook.

Air Ride Suspension

An air ride suspension is a suspension which supports the load on air-filled rubber bags rather than steel springs. Compressed air is supplied by the same engine-driven air compressor and reservoir tanks which provide air to the air brake system.

Axle, Single

A single axle is one axle mounted independently of any other axle.

Axle, Spread Tandem

A spread tandem axle is a two-axle assembly in which the axles are separated beyond the spacing of a normal tandem assembly in order to qualify for maximum axle loads allowed by regulations.

Axle, Tandem

A tandem axle is a two-axle assembly having a means of distributing or transferring weight between the two axles.

‘B’ Train

A ‘B’ train is a tractor pulling two semi trailers. The lead unit having a fifth wheel at the back to attach the second semi trailer or pup.


A bobtail is a tractor operating without a trailer. Also refers to straight truck.


A bogie is an auxiliary axle assembly having a fifth wheel used for purpose of converting a semi trailer to a full trailer. Dollies can be used to haul multiple trailers behind a single power unit. (Also referred to as dolly).


The control room on a truck where the driver sits.

Combination Vehicle

An equipment configuration which includes separate power unit (tractor) and at least one trailer.

Commercial Trailer

A trailer used to handle freight in the transportation of goods for others; excludes house trailers, light farm trailers and car trailers.

Curb Weight

See Chassis Weight.

Chassis Weight

See Tare Weight.

Double Drop

A trailer used for flatbed trucking (stepdeck) whose deck drops at the rear, ahead of the tires as well as at the front of the trailer, but deeper than a single drop. This puts the deck closer to the ground than a single drop as the deck drops below the top of the tires.


An auxiliary axle assembly having a fifth wheel used for purpose of converting a semi trailer to a full trailer. Dollies can be used to haul multiple trailers behind a single power unit. (also referred to as Bogie)


A combination of two trailers pulled by a power unit. Usually refers to a power unit pulling two 28′ trailers. See also Rocky Mountain Double and Turnpike Double.

Dry Van

A van that doesn’t have a reefer unit.

Extendable Flatbed Trailer

A trailer used for flatbed trucking whose length may be readily increased or decreased within prescribed limits and with prescribed variations in load carrying capability. Used mainly for oversized loads.

Fixed Tandem

Assembly of two axles and suspension that is attached to the chassis in one place, and cannot be moved fore and aft.


A flatbed or flat deck is an open trailer used in flatbed trucking. It is made of wood or metal and is used for carrying cargo.


On a drop frame trailer, that portion of the trailer which extends upward and forward from the front of the loading deck to, and including, the upper coupler and front crossmember.

Gooseneck, Removable

A gooseneck which can be separated from the trailer and reconnected, usually through the use of large hooks or removable pins. The motive force required to remove such goosenecks is usually obtained through the use of the tractor winch line or hydraulic cylinders.


A trailer with a flat deck.

Highway Tractor

A tractor is the power unit used for pulling trailers on the highway.


Any of several materials, or classes of materials, used in the construction of trailers and containers whose function it is to control the transfer of heat in or out of the vehicle.


A kingpin is an anchor pin at the center of a semi trailer’s upper coupler which is captured by the locking jaws of a tractor’s fifth wheel to attach the tractor to the semi trailer.


An LCV (Long Combination Vehicle), in general, is a vehicle longer than a standard doubles rig (tractor and two 28-foot semi trailers). Examples of LCVs which are permitted in some U.S. western states and eastern toll roads: Twin 48-foot trailers; triple 28-foot trailers.

Load Bars

A tool used to secure freight in a trailer.

Load Binder

A mechanical device, consisting of a lever-operated toggle and lock, generally used to tighten a cargo securing system. Winches are sometimes used as load binders.

Load Straps

Canvas belts, used in flatbed trucking, that are long enough to go over the top of a load and used to hold the cargo onto the deck of a flatbed trailer. Load straps are also used on the inside of an enclosed van to secure freight.


Book carried by truck drivers in which they record their hours of service and duty status for each 24-hour period.


A lowboy, used for flatbed trucking, is an open flatbed trailer with a deck height very low to the ground. It is often used to haul construction equipment or bulky or heavy loads.


Term that refers to the front of a trailer


Structural load-carrying members attached to and extending outward from the main longitudinal frame members of a trailer.

Pintle Hook

Coupling device used in double trailer, triple trailer and truck-trailer combinations. It has a curved, fixed towing horn and an upper latch that opens to accept the drawbar eye of a trailer or dolly.

Power Units

The control and pulling vehicle for trailers or semi trailers.

Pup Trailer

Short semi trailer usually between 26 and 32 feet long with a single axle.


Removable wood or metal wall sections (usually slatted) held in place on flatbeds normally by stake pockets.


Articulated or removable bridge-type structures used to load or unload lowbed or drop frame trailers.

Red Line

Term referring to the halfway point in a trailer. The line is painted across the top inside ceiling of the trailer.

Refrigeration Unit

A mechanical device designed to be mounted on a refrigerated trailer or shipping container for the purpose of cooling the cargo area.

Rocky Mountain Double

A combination vehicle consisting of a tractor, a 45 to 48 foot semi trailer and a shorter 28 foot semi trailer.


Device that is serially numbered and used to temporarily fasten trailer and truck doors so that unauthorized entry into the unit can be detected.

Semi Trailer

Truck trailer equipped with one or more axles and constructed so that the front end rests upon a truck tractor.


Sleeping compartment mounted behind a truck cab, sometimes attached to the cab or even designed to be an integral part of it.

Stepdeck / Single Drop

A stepdeck trailer, used by flatbed companies, has a main deck that is lower than the deck above the fifth wheel, but not as low as that of a double drop. The back of the deck is usually level with the top of the trailer tires.

Straight Truck

A vehicle with the cargo body and tractor mounted on the same chassis.

Tare Weight

Weight of the empty truck, without occupants or load.

Tarp / Tarpaulin

Tarps are water resistant fabric covers used by flatbed trucking companies to protect the cargo on an open trailer.

Tractor Trailer

Tractor and semi trailer combination.


A vehicle designed without motive power, to be drawn by another vehicle.


Truck, tractor or trailer with three axles grouped together at the rear. (Also referred to as a tridem.)


A motor vehicle designed to carry an entire load. It may consist of a chassis and body; a chassis, cab and body; or it may be of integral construction so that the body and chassis form a single unit.

Turnpike Double

A combination vehicle consisting of a tractor and two trailers of 45 to 48 feet.

Twin Trailer

A short semi trailer (under 29 feet) designed to be operated as part of a combination vehicle with a tandem trailer of similar length.

Van (Dry Van)

Standard trailer or truck with all sides enclosed.

Yard Jocky

A yard jockey is a person who operates a yard tractor.

Yard Tractor

Special tractor used to move trailers around a terminal, warehouse, distribution center, etc. (Also referred to as a yard mule.)
Get a Rate Quote | Ship North America