Trucking Terminology and Transportation Definitions

Trucking Terminology

ABS (Anti-lock braking system)

The ABS system helps the driver retain control of the vehicle under heavy braking conditions.

Air Brake

A brake which is operated by air. The air brake system on tractors consists of air lines, valves, tanks, and an air compressor.

Air Ride Suspension

The suspension system supports the weight of the load, plus the trailer on air filled rubber bags rather than the old system
which used steel springs. The compressed air is supplied by the air compressor and reservoir tanks which provide air for
the air brake system.

Air Spring System

The system in which the container and plunger are separated by pressurized air. When the container and plunger attempt to
squeeze together, the air compresses and produces a spring affect.

Air Tank

A reservoir for storing air for use in the air brake system. Braking would be impossible without an adequate supply of air.


A structural component to which wheels, brakes, and suspension are all attached.

Types of axles:

  • Steer Axle: the front axle of the tractor.

  • Drive Axles: axles with powered wheels.

  • Pusher Axles: unpowered, go ahead of drive axles.

  • Tag Axles: unpowered, go behind drive axles.

  • Rear Axles: may be drive, pusher, or tag axles.

  • Trailer tandem axles: generally unpowered, sometimes split apart for distribution.

Back Haul

A return load. Many companies, often ones who haul their own product, take a load from their home location to a certain
area the country, then they need to go back to the original location to pick up another similar load. Instead of returning
empty, they’ll find another load (the “back haul”) going back to the original location.

Bill of Lading

Shipping documents or shipping papers for a particular shipment. It contains an itemized list of goods included in the shipment.
It also serves as a contract of shipment, and a receipt for the goods.

Blind Spot

The areas around a tractor-trailer which are not visible to the driver through the windows or mirrors.


The tractor operating without a trailer attached.


The assembly of two or more axles, often a pair in tandem.

Balloon Freight

Cargo which takes up a lot of space, but is very light.

Bridge Formula

A bridge protection formula used by federal and state governments to regulate the amount of weight that can be put on each
of a vehicles axles, and how far apart the axles must be to legally be able to carry a certain weight.

Bulk Freight

Freight that is not in packages or containers; normally hauled in tankers, grain trailers, and sometimes in regular van


Short for cab-over-engine, designed so that the cab sits over the engine on the chassis.

Cartage Company

A motor carrier that provides local pickup and delivery.

CAT Scales

The most common type of scales at truck stops are CAT scales. These are purported to be the most accurate, and they guarantee
the weight reading to be accurate, or else they’ll go to court for you and pay the fine.

CB (Citizens Band Radio)

The type of radio that’s used by truckers to communicate with each other.

CDL (Commercial Drivers License)

The drivers license which authorizes individuals to operate commercial motor vehicles and buses over 26,000 pounds gross
vehicle weight.

Check Call

Calling by telephone, or using the Qualcomm system to check in with your company/dispatcher, usually once a day, early in
the morning. This informs them of your progress, and any other important information a company may require.

Clearance Lights

The lights on top of the front and rear of the trailer; often referred to as the marker lights.

Clutch Brake

The clutch brake is engaged when you push the clutch all the way to the floor. You only do this when you’re stopped, and
need to get the truck into gear.


The company that issues Comchecks and Comcard.

  • Comcheck: blank checks you receive from your company to get cash advances when you’re on the road, or for certain truck
    expenses, lumpers, etc. When you need a cash advance, you tell your dispatcher how much money you need, and he gives you
    a code to place on the check. This is a reference number the truck stop (or wherever you’re getting the cash advance) uses
    to verify that the check is good.

  • Comcard: a fuel card you’re issued by your company for you to use for fuel, oil etc.. Also can be used to receive cash advances.

Commentary Driving

Many truck driver training programs utilize the commentary driving concept. This is an important tool to help the student
understand both how a truck driver thinks and sees things as he drives down the road, and how the student will have to modify
his own thinking in order to be a safe and effective truck driver. While training, the trainer first drives down the road
while verbalizing everything he is thinking, seeing, and doing. This is done to give a clear example of what is required
of the driver in the day-to-day operations of a big truck. Then the student takes a turn driving and openly verbalizes what
he’s thinking about and exactly what he’s seeing so that the trainer and other students can hear and evaluate his observations,
while comparing the two different approaches.


A shipping container is a standard sized metal box used to transport freight. It is used in Intermodal Transportation, which
utilizes different modes of transportation ship, rail, and highway. International shipping containers are 20 to 40 feet long,
and have to conform to International Standards Organization (ISO) standards and are designed to fit in ship’s holds. Containers
are transported on public roads on a container chassis trailer pulled by a tractor. Domestic containers are up to 53 foot
long, and are of lighter construction; these are designed for rail and highway use only.

Container Chassis

A type of trailer specifically designed to carry a shipping container.


A style of tractor in which the cab sits behind the engine compartment, instead of over it (as in the case of the Cabover)

Converter Dolly

The assembly which connects trailers together, as in a set of double or triple trailers. This assembly is equipped with
the fifth wheel for coupling.


The receiver, who accepts your delivery.


This is the capacity, measured in cubic feet, of the interior volume of a trailer.

DAC Services

A pre-employment screening service many trucking companies use to help them select drivers.

Day Cab

A tractor which has no sleeper berth. Often for local work where the driver gets home every night.


Driving a tractor-trailer without cargo, or without paying load.


Extra driver pay for time spent waiting at a customer facility.

Dock Lock

A safety device that hooks to your trailer’s bumper when you’re backed to a loading dock. This device is controlled from
inside the facility, and it prevents the trailer from being able to move away from the dock, especially considering the safety
of the forklift driver and anyone else inside the trailer. See the section on ” picking up the load”.

Drop and Hook

Taking a loaded trailer to a shipper/receiver, dropping the trailer (unhooking the trailer, and leaving it there at the
customer’s facility), and then hooking up to, and leaving with, another loaded trailer. Most drivers prefer this because
there’s no waiting, sometimes for hours, for your trailer to get unloaded or loaded.

Drop Pay

Extra pay for a delivery, usually an extra stop.

Dry Freight

Freight that’s not refrigerated.

Empty Call

The call you make to your dispatcher to inform him that you’re unloaded/empty, and need a new load assignment.

Fifth Wheel

The coupling device attached to a tractor or dolly which supports the front of the semitrailer and locks it to the tractor
or dolly. The center of the fifth wheel hooks to the trailer’s kingpin, at which point the trailer and tractor or dolly pivots.


A common term for what a driver does when he has to unload the trailer by himself.

Fixed Tandem

The assembly of two axles and suspension that is attached to the chassis in one place and cannot be moved back and forth.

Floating the Gears

When you shift gears without using the clutch.


The cargo you’re hauling. The same as product, commodity, load, etc.

Freight Lane

The route, often an Interstate or major highway, on which a great amount of freight flows back and forth. If you work for
a company which uses regular freight lanes, it will be beneficial to your home time if you live on or near one of these freight

Frequent Fueler

Many of the major truck stops have frequent fueler programs or cards which drivers can sign up for. These programs give
you credit or cash back for each gallon of fuel you purchase.

Full Trailer

A trailer supported by axles on the front and on the rear of the trailer.

GAWR (Gross Axle Weight Rating)

The maximum weight an axle is rated to carry by the manufacturer. Includes both the weight of the axle, and the portion
of a vehicle’s weight carried by the axle.

GCW (Gross Combination Weight)

The total weight of a loaded combination vehicle, such as a tractor-trailer.

Georgia Overdrive

Taking the truck out of gear when you’re going down a hill, which enables the truck to go extremely fast. Not only not recommended,
but certainly grounds for immediate termination.


Government Bill of Lading.


A device which limits the maximum speed of a vehicle. Used by a great number of trucking companies who want to save on fuel
expenses, and limit accidents.


A significant change of elevation; either an upgrade, or downgrade, the steepness of which is determined as a percentage.
For example, a road with a 5% downgrade decreases 5 feet for every 100 feet of travel.


A vehicle’s ability to climb a certain percentage of grade at a given speed. For example, a truck with a gradeability of
6% at 60 mph can maintain 60 mph on a 6% grade.

GVW (Gross Vehicle Weight)

The total weight of a vehicle; the vehicle’s weight, and the contents of the trailer and tractor.

GVWR (Gross Vehicle Weight Rating)

The total weight a vehicle is rated to carry by the manufacturer, including it’s own weight and the weight of the load.


Hazardous materials, as classified by the United States Environmental Protection Agency (EPA). Any transportation of hazardous
materials is regulated by the United States Department of Transportation. To haul hazardous materials, a driver needs a hazmat
endorsement on his CDL, plus special training.

Headache Rack

A metal barrier station behind the tractors cab, to prevent loads from coming forward and crushing the tractor (and anyone
inside). Most common on tractors pulling flatbed trailers.


When the tires lose contact with the road due to excess water.

Interaxle Differential

On tractors with tandem rear axles, the interaxle differential allows each axle to turn independently.


When the tractor is at an extreme angle to the trailer. Can be done intentionally, as in jackknife parking, or unintentionally,
as in a jackknife accident common when slippery conditions are present.

Jackrabbit Start

Releasing the clutch too quickly, which causes the vehicle to jerk forward.

Jake Brake

An engine retarder which helps to slow vehicles, especially on down grades.

Johnson Bar

The trailer hand valve, commonly used to test the brakes after coupling the tractor and trailer. Also known as the trolley


A thick, metal pin located underneath the front of the trailer. This kingpin slides into, and connects with, the locking
jaws of the fifth wheel of the tractor or dolly, thereby attaching the tractor/dolly to the trailer.

Kingpin Lock

A locking device which is placed around/over the kingpin, which prevents a fifth wheel from connecting to it, and taking
the trailer. Highly recommended if you plan on dropping the trailer in an unsecured location, which includes truck stops.

Landing Gear

Retracting legs which support the trailer when it’s not connected to a tractor.


Any off-duty time while away from home.

Loaded Call

The call you make to your dispatcher from the shipper once your trailer is loaded, and the bills are signed.

Lift Axle

An extra, unpowered axle which is needed only when the vehicle is loaded, and which allows it to meet Federal and state
vehicle weight standards. The axle can be raised or lowered by an air spring suspension system.


Moving freight from one point to another.

Load Locks

Long metal bars which retract and expand to fit in place from one side wall of the trailer to the other, thereby holding
back, and securing the load (cargo).

Log book

The book in which truck drivers record their trucking activities — a truck driver’s hours of service and duty status for
each 24-hour period. Details of maintaining your logbook are covered in a different section.

LCV (Long Combination Vehicle)

Any combination of a truck tractor and two or more trailers or semi-trailers which operate on the Interstate System at a
gross vehicle weight (GVW) greater than 80,000 pounds.

Low Boy

An open flatbed trailer, where the main body of the trailer is very low to the ground so that it can haul oversize or wide
loads; often construction equipment, or other extremely bulky or heavy loads.

LTL (Less-Than-Truckload)

A quantity of freight less than that required for the application of a truckload rate, usually less than 10,000 pounds.
These smaller loads are consolidated by an LTL carrier into one vehicle headed for multiple destinations.


Casual laborers who load and unload trailers for a fee.

MVR Report

A driver’s motor vehicle record, which shows all violations, accidents, etc.


Any shipment which is under 100 pounds.

No Touch

A situation in which the driver doesn’t have to load or unload (no touching, or fingerprinting, the load) the cargo.

Omnitracs, formerly Qualcomm

A satellite tracking device and communication tool that can also be used to monitor speed, braking, idling, and other barometers

Opti- Idle

Equipment which starts and shuts down the truck to keep the truck a certain temperature inside, while reducing idling time.

O,S,& D Department

The Department of your company which handles overage, shortage, and damaged cargo. See the section on OS & D in “at the

Out of Route

Motor carriers usually use set mileage amounts for distances between cities. If a driver goes over this amount, any miles
over the set amount are considered “out of route” miles.


Extra freight which shouldn’t have been shipped.


A truck driver who’s in business for himself; and owns and operates his own truck/s, trailer/s, and/or equipment; an independent


Pickup and delivery operations.


The wooden base onto which a product is loaded. It has slats on the sides which enable a forklift to move products easily.

Pay Load

The weight of the cargo being hauled.

Peddle Run

A load which has multiple, and often frequent deliveries.


A semi- trailer built with reinforcements to withstand transport by a railroad flatcar.


The term used for the situation in which loaded highway trailers are loaded onto railcars, and taken to railheads. From
there, local trucks take the trailers the rest of the way to their destination.


The electrical line supplying electric power from the tractor to the trailer, coiled like a pig’s tail.

Pintle Hook

A coupling device used in double and triple trailer, and truck-trailer combinations.


A sign showing the type of hazardous materials loaded on the vehicle, placed on all four sides of a trailer.

Power Divider

See “Interaxle Differential”.

Private Carrier

A business which uses its own trucks to transport its own products and/or raw materials.

PTO (Power Takeoff)

A device used in tractors which transmits tractor engine power to auxiliary equipment.

Public Scales

The scales the general public is able to use to weigh their vehicles.

Pull Trailer

A short, full trailer (supported by axles on the front and rear of the trailer), with an extended tongue.

Pup Trailer

A short semi-trailer, usually between 26 and 32 feet long, and having only a single axle at the rear.

Qualcomm (now Omnitracs)

A satellite tracking device and communication tool that can also be used to monitor speed, braking, idling, and other barometers
of a driver’s efficiency.


The customer who accepts your delivery/shipment; Also known as the consignee.

Relay Driving

In LTL shipments, a driver only takes a load a portion of the way, usually for the duration of one shift (eight to 10 hours).
The driver then turns the truck over to another driver to continue the trip.


A refrigerated trailer, where the temperature is controlled by a refrigeration unit (the reefer unit). A “reefer” can either
refer to the reefer unit or the entire reefer trailer.


The device used to assist brakes in order to slow a vehicle. There are many different types of retarders; including engine
retarders, transmission-mounted hydraulic retarders, and axle mounted electromagnetic retarders. An engine retarder commonly
called a ‘Jake Brake’ is used in most trucks today.

Rider Policy

The company’s policy regarding allowing passengers in the truck with the driver.

Runaway Truck Ramp

An emergency escape ramp used on steep downgrades for trucks which have lost braking power.

Ryan Recorder

A monitoring and recording device which is placed inside of a temperature controlled trailer.


A plastic or metal band (once it’s broken, it cannot be reconnected) placed on the trailer door latch. An intact seal ensures
that the trailer doors have not been opened, and the cargo is untouched.


A trailer supported at the rear by its own axles and wheels, and at the front by fifth wheel from a tractor or dolly.

Service Plaza

A rest area found on turnpikes or toll roads. These usually have truck parking, restrooms, vending machines, telephones,
and often fast food restaurants.


A local delivery, or trailer movement.


A sleeping compartment situated behind the tractor’s cab, behind the driver’s seat, or an integral part the cab.

Sliding Tandem

A mechanism that allows a tandem axle suspension to be moved back and forth at the rear of a semi-trailer in order to distribute
the weight between axles, and adjust the length between kingpin and tandems.

Sliding Fifth Wheel

A fifth wheel with a sliding mechanism which allows it to be adjusted in order to distribute the weight of the axles, varying
the overall vehicle length and weight per axle.


When a driver is not assigned to a regular tractor, but moves in and out of tractors as they become available.

Space Cushion

The area between the vehicle and other vehicles on the road. It is important to keep an adequate space cushion to avoid
accidents, etc.

Spread Axle

A tandem axle assembly that has the ability to be spread farther apart than the standard spacing. When the tandems are spread
to 8 or 9 feet, each axle is weighed independently, with each allowed up to 20,000 pounds (or 40,000 pounds for the combined
tandem weight).


A yard driver who moves and parks trailers in a terminal yard (In some places, they’re known as a ‘yard dog’ or ‘yard jockey’).
The vehicles used to move the trailers are designed so that the driver just walks behind the driver’s seat to hook up the
airlines, and includes a hydraulic lift to lift up the trailer without having to crank up the landing gear, so that the trailers
can be moved quickly.

Tandem Axle

A pair of axles grouped closely together; either the drive axles on the tractor or the tandem axles of the trailer.

Team Driving

Two drivers who alternate between driving and non-driving time (sleeping, resting, etc) in order to expedite the shipment
and maximize the overall production of the truck.

TL (Truckload)

A quantity of freight sufficient to fill a trailer, usually greater than 10,000 pounds.

TL Carrier

A trucking company which usually dedicates trailers to a single shippers cargo, as opposed to an LTL carrier, which often
transports the combined cargo of several different shippers.


A truck designed primarily to pull a semi-trailer by the use of the fifth wheel which is mounted over its drive axle/s.
May be called a truck/highway tractor to differentiate it from a farm tractor.


Any combination of three axles grouped together.

Trip Leasing

The term used for the practice of contacting other trucking companies in an area where a driver needs a load, and selecting
from available ‘overbooked’ loads.


A tractor which carries cargo in a body (van, tank, etc.) which is mounted to its chassis, possibly in addition to a trailer
which is towed by the tractor. This is common in truck-trailer combination vehicles which haul fuel, or other liquid.


A truck-trailer combination consists of a truck which holds cargo in its body which is connected to its chassis, and which
tows a trailer.

WIM (Weigh-In-Motion)

The system which allows a vehicle to be weighed while still in motion on the interstate, usually just before coming to a
weigh station.

Transportation Definitions

Motor Carrier

A company that provides truck transportation. There are two types of motor carriers, private carriers and for-hire carriers.

Private Carrier

A company that provides truck transportation of its own cargo, usually as a part of a business that produces, uses, sells
and/or buys the cargo being hauled.

For-Hire Carrier

A company that provides truck transportation of cargo belonging to others and is paid for doing so. There are two types
of for-hire carriers, common carriers and contract carriers. A for-hire carrier may be both a common and a contract carrier.

Freight Forwarder

A company that arranges for the truck transportation of cargo belonging to others, utilizing for-hire carriers to provide
the actual truck transportation. The Forwarder does assume responsibility for the cargo from origin to destination and usually
does take possession of the cargo at some point during the transportation. Forwarders typically assemble and consolidate
less-than-truck load (LTL) shipments into truckload shipments at origin and disassemble and deliver LTL shipments at destination.


A company that arranges for the truck transportation of cargo belonging to others, utilizing for-hire carriers to provide
the actual truck transportation. However, the Broker does not assume responsibility for the cargo and usually does not take
possession of the cargo.

Note: These trucking definitions are simplified. Legally acceptable definitions of these activities would be longer, more complex, and supported by the results of many administrative proceedings, court decisions and judicial opinions. If there is any question about the applicability of these simplified definitions, a legal authority should be consulted.

Go to top of page