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Commercial Driver License Glossary of Terms

CDL Testing Terminology

The term CDL refers to a Commercial Driver License in the United States. We define the common terms.

The CDL Written Test

You must pass a written CDL test and a hands on CDL Skills test in order to obtain your Commercial Driver's License. The written test can only be taken at the Department of Motor Vehicles. You will need to obtain a CDL Manual for the written test. For your convenience you may obtain one online. We have an excellent online course to help you with your studies.

The CDL Skills Test

DMV offices no longer provide the CDL skills test. The CDL skills test consists of a pre-trip inspection, backing maneuvers and a road test. In order to take the CDL Skills test, you must have a valid CDL instruction permit for the appropriate vehicle class. Training is not required to take a skills test.

The CDL Permit

You pass a series of CDL Written Tests at your Motor Vehicle.  You must have a Department of Transportation Physical in addition to passing the written tests before receiving your CDL Learners Permit.

The CDL Permit allows you to drive a commercial vehicle with a  licensed CDL Driver. Similar to a 15 year old learning to drive with their parents.

All Trucking Terms Glossary


"A" DOLLY- this converter dolly has an "A" shaped drawbar that joins at a single connection point to the trailer ahead of it. These dollies can have one or more axles and are the most common in use.

ABS (Anti-lock Braking System) will sense wheel speed and modulate braking force if wheels lockup during braking. ABS can help the driver retain control of the vehicle during heavy braking on slippery roads.

"A" DOLLY - this converter dolly has an "A" shaped drawbar that joins at a single connection point to the trailer ahead of it. These dollies can have one or more axles and are the most common in use. See DOLLY.

AIR CAN TRAILER - (Slang) pneumatic tank trailer for transporting solids in bulk

AIR FREIGHT CONTAINER - a smaller and lighter cargo container often made out of fiber glass designed to hold cargos that are shipped in airplanes.

AIR LIFT AXLE, or LIFT AXLE - an air-powered axle which, when lowered, will both convert a vehicle into a multi-axle unit and provide greater load carrying capacity

ARTICULATED BUS - usually more than 55 feet in length, characterized by two connected passenger compartments that bend or flex in the middle and allow the bus to maneuver through curves or around corners.

ARTICULATION - the space between the power unit and trailer that allows the combination to pivot and turn corners.

"A-TRAIN" - (Slang) a truck tractor pulling more than one trailer connected by "A" dollies

AUGER - a shaft with a broad spiral flange rotating inside a cylindrical casing to carry bulk material from one end of the shaft to the other. Augers are used to unload cargoes such as grain from grain trailers.

AUTO CARRIER - this cargo body style is typified by the multi-decked auto carrier trailer and/or power unit.

AXLES - (1) a vehicle component to which wheels, brakes, and suspension attach; (2) axle designations such as "4x2," "6x4," etc.: the number of wheels followed by the number of wheels driving, each axle assumed to have one wheel at each end, e.g., 6x4 is 6 wheels total, 4 driving, thus, a 3-axle power unit with 2 drive axles.

AXLE WEIGHT - amount of weight carried by one axle.


"B"DOLLY - a fifth wheel mounted on one or more axles that are permanently attached and extend off the rear of a semitrailer, most commonly used on flatbeds or tank trailers.

BAFFLE - a wall or partition inside a liquid tank that inhibits the flow of fluids reducing the slosh effect that liquid tankers experience.

BBC (Bumper to Back of Cab) the distance from the front bumper to the back of the truck cab.

BEAVERTAIL - refers to hinged ramps on the end of a flatbed trailer enabling vehicles or heavy equipment to drive onto the trailer. These ramps can be powered by a hydraulic mechanism.

BELLY BIN - boxes attached under the floor of a trailer, can carry cargo, but more often for carrying spare parts or dunnage.

BELLY DUMP - another name for a HOPPER BOTTOM trailer, both empty from underneath via gravity.

BIG COWL AND CHASSIS BUS TYPE - a type of bus depicting non school bus coaches mounted on a truck-based, flat back cowl (medium- or heavy-duty truck hood and fender assembly).

BILL OF LADING - a contract between the shipper and the carrier that includes freight origin and destination, description, and weight.

BOBTAIL - (Slang) a tractor with no trailer. Sometimes straight trucks with no trailer are also referred to as bobtails.

BOOM - a lifting mechanism. May be mounted on or as part of the cargo body of a truck. Booms are common on utility trucks or flatbeds.

BOOSTER DOLLY - usually at the rear of a truck or LCV and employs hydraulics to shift some of the load weight onto the rear dolly axles

BOTTLE - refers to the cargo tank of a truck or trailer designed to carry liquefied or compressed gases. Examples include bottled gas, propane, and butane.

BOTTOM DUMP - dry bulk bodies which empty by means of gravity alone through the bottom. Sometimes referred to as hopper-bottoms or belly dumps

"B-TRAIN" - (Slang) a truck tractor pulling two semi trailers where the second trailer sits on a fifth wheel that is permanently attached and extends off the rear of the lead trailer. Most commonly used on flatbeds or tank trailers. The "B"train is considered a more stable double trailers configuration.

BTS (Bureau of Transportation Statistics)

BUILDING MATERIALS - this cargo category is for bricks, blocks, cement in bags, wallboard, insulation, and mixed cargoes of these in addition to lumber, paint, hardware, and other materials are included.

BULK CARGO - loose and unpackaged, sometimes referred to as aggregate cargo.

BULKHEAD - wall-like structure used at the front of a flatbed or back of the power unit to protect against damage from shifting cargo, or a wall inside any trailer that partitions the load.

BULK TRUCK or TRAILER - a vehicle that can carry loose cargos in bulk. It usually refers to solids in bulk.

BUNK - cradle-like metal up-right brackets mounted on a log truck or trailer to hold the logs. Sometimes referred to as bolsters.


CC, or C & C - (Cab and Chassis).

CA - (rear of Cab to rear Axle) measurement.

CAB - normally the enclosed compartment in a vehicle in which the driver sits.

CAB FORWARD - similar to a cabover in that the cab is positioned ahead of the engine. Most commonly seen on refuse trucks and some construction equipment.

CAE - (Cab Aside Engine) seen on refuse trucks and some construction equipment.

CB, CBE - (Cab-Behind Engine). conventional, has a hood and an engine in front of the

CDL - (Commercial Drivers License) a license that authorizes an individual to operate a specific class of commercial motor vehicles.

"C" DOLLY - this converter dolly has two drawbars and attach at two connection points to the trailer ahead of it. These dollies can have one or more axles and are considered more stable than the common "A" dolly.

CHARTER BUS - a bus that is operated on a for-hire basis, usually providing round-trip service for a tour group or an outing, either on an ad hoc or scheduled basis.

CHASSIS - refers to the frame of any vehicle, or to describe type of semitrailer for transporting lift-off containers.

CHASSIS CAB - most trucks are sold as a frame (chassis) with a cab. The cargo body or fifth wheel is added by the purchaser or a "body builder."

CHEATER AXLE - (Slang) for a lift axle or an air-powered axle which, when lowered, will both convert a vehicle into a multi-axle unit and provide greater load carrying capacity.

CLUB CAB - a two door truck cab with a back seat behind the front seats.

CMV (Commercial Motor Vehicle ) - a motor vehicle or combination of motor vehicles used in commerce to transport passengers or property if the motor vehicle: 1) has a gross combination weight rating greater than or equal to 26,000 lb. including a towed unit with a gross vehicle weight rating of at least 10,000 lb.; or 2) has a gross vehicle weight rating of at least 26,001 lb.; or 3) is designed to transport 16 or more passengers including the driver; or 4) a motor vehicle of any size that transports hazardous materials of any kind.

COAL TRAILER - usually refers to a dump trailer, or a coal hopper bottom. AKA coal bucket.

COAL TRUCK - usually refers to a dump truck used to haul coal. AKA coal bucket.

CABOVER/COE- (Cab-Over-Engine) power unit, as opposed to the conventional cab located behind the engine. The cabover is identified by the windshield being located directly over the front bumper and driver more or less directly over the steering axle. Sometimes referred to as "flat-faced" or "butt-nosed."

COMBINATION VEHICLE - a vehicle made up of two or more separate units hooked together, such as a tractor-semitrailer combination. Also called an ARTICULATED vehicle since units pivot at the coupling point.

COMMODITY - anything bought and sold.

COMMON CARRIER - a transportation business that offers service to the general public. Interstate common carriers must hold a certificate issued by the Interstate Commerce Commission which limits service to a specific geographical area.

COMPACTOR - a device used to compact things, particularly garbage.

CONSIGNEE - the person or firm designated to receive freight that has been shipped.

CONSIGNOR - the person or firm responsible for shipping a particular freight.

CONTAINER CHASSIS - a truck or trailer chassis consisting of a frame (no floor, sides or roof) with locking devices for securing and transporting a container.

CONTRACT CARRIER - a company that engages in for-hire transportation of property under individual contract or agreement with one or a limited number of shippers.

CONVENTIONAL - engine forward of cab in power unit. Snub nosed, short hooded cabs are conventional. Step vans are conventional.

CONVERTER DOLLY - an undercarriage assembly with one or more axles, a fifth wheel, and a tongue, used to convert a semitrailer to a full trailer.

CONVERTER GEAR - (Slang) synonymous with converter dolly.

CRAWLER - an off-road vehicle utilizing track propulsion instead of wheels.

CREW CAB - a four door truck cab with front and back seats.

"C-TRAIN" - (Slang) a truck tractor pulling more than one trailer connected by "c" dollies.

CUBE - as in "cube out before grossing out", refers to cubic cargo area space. Can also be used to refer to a pallet of concrete blocks.

CUBE VAN - typically a straight truck with a van style cargo body where the width and height of the cargo body exceed that of the truck cab.


DAY CAB - a truck or tractor without a sleeper birth. Typically used for day trips or local routes.

DBA - (Doing Business As) - common usage for a business license.

DEAD AXLE - non-powered rear axle on tandem truck or tractor.

DEAD HEAD - a trip where the tractor pulls an empty trailer or a trailer loaded with cargo that generates no revenue.

DECK SET - (Slang) for piggyback hauled trucks. See piggyback/towaway.

DITCH WITCH - brand name of a machine which digs trenches.

DOUBLES "A" TRAIN - (Slang) a truck tractor pulling more than one trailer connected by "A" dollies.

DOUBLE BOTTOM - (Slang) a combination vehicle consisting of a tractor pulling a semitrailer and a full trailer.

DOUBLES "B" TRAIN - (Slang) a truck tractor pulling two semi trailers where the second trailer sits on a fifth wheel that is permanently attached and extends off the rear of the lead trailer. Most commonly used on flatbeds or tank trailers. The "B"train is considered a more stable double trailers configuration.

DOUBLES "C" TRAIN - (Slang) a truck tractor pulling more than one trailer connected by "C" dollies.

DOZER - a blade used to move material by pushing. The vehicle itself is often called a dozer, and it may be tracked or wheeled.

DRAW BAR - typically a metal bar that connects a truck and trailer. Sometimes referred to as the tongue of the trailer.

DRIVE AXLE - any axle that carries power from the engine to the wheels that propel a truck or tractor. See AXLE

DOUBLE DROP DECK - a trailer, usually a flatbed, with a floor set at three different heights, it steps down towards the middle and then steps back up at the rear. Sometimes referred to as a STEP DECK.

DUAL WHEELS - four wheels per axle rather than two.

DUMP - a cargo body with a hydraulic, electric, or mechanical lifting mechanism that tilts to unload cargo. DUMP includes side dumps, walking dumps, flatbed dumps, and dump trucks with snow plows or blades.

DUMPSTER - a large metal container for garbage. The term is sometimes used to describe refuse trucks. Dumpsters are different from a roll-off containers. A dumpster is usually kept at a garbage collection point and not carried on a refuse truck. Some refuse trucks carry dumpsters short distances for loading, unloading, or distribution.

DUNNAGE - loose materials (like padding) used around cargo to prevent damage.


EIGHTEEN WHEELER - (Slang) most commonly a combination vehicle consisting of a three axle tractor pulling a two axle semitrailer or a two axle tractor pulling a three axle semitrailer.

EQUIPMENT LOADER or EQUIPMENT DUMP - refers to equipment hauling flatbeds.

ELECTRONIC TRIP RECORDER - a device for recording data on a vehicle's performance, originally designed for monitoring and optimizing engine performance, in recent years GPS systems have been added to enable dispatchers to geo-locate their trucks and many trip recorders maintain HOS data, eliminating the need for driver maintained logbooks.

EXEMPT - free from ICC rules regulating other cargos transported by interstate for-hire carriers.

EXPANDABLE - flatbed or pole trailers that can be expanded beyond its regular length to carry larger shipments.


FAK - (Freight of All Kinds) - an acronym for mixed general freight in the back of a truck or trailer. See LTL.

FARM PRODUCTS - this category is for unprocessed items which were grown in or produced from agricultural activity on a farm or in a garden, nursery, or orchard. Articles manufactured or processed from these commodities are not included in this category.

FARS - (Fatality Analysis Reporting System) operated by the National Highway Traffic Safety Administration (NHTSA).

FLAT FACE - cab over engine.

FLAT FRONT BUS TYPE - depicting typical transit and shuttle buses. Flat-nosed buses, can either be front, mid-ship or rear engine. Most non-articulated transit versions are rear engine; articulated versions may have the engine in the rear of the second unit (true pushers) or mid-ship, at the rear of the first unit. Can be low floor configuration (level floor area to front of vehicle fairly even with curb height) or standard platform (about 2-3 steps from curb to passenger platform. Some transit buses have a kneeling feature, fold-out ramps, or even may be equipped with a lift to accommodate special needs passengers. No cargo capacity under floor.

FOR HIRE MOTOR CARRIER - is a transporter of (other people's) property…by motor vehicle for compensation.

FORKLIFT - an off-road vehicle with 'forks' for lifting and moving crates. There are warehouse and rough-terrain forklifts. AKA hi-lo.

FRAME CONSTRUCTION - a type of trailer construction in which the weight of the load is transmitted through the cross members and outriggers directly into the main frame, rather than borne by the sides of the trailer.

FRONT AXLE - usually has a single wheel on either side of the truck that steer the vehicle.

FRONT END LOADER - an off-road vehicle, with a forked loading device in front.

FRONT-LOADER - a refuse truck that is loaded at the front usually has hydraulic arms that lift dumpsters over the cab dumping their contents into a bin with some kind of compacting mechanism. Arms must be included in truck length.

FUEL - type of fuel used can be gasoline, diesel, CNG (compressed natural gas), LPG (liquefied petroleum gas, also referred to as propane), or other (electric, hybrid etc.). Specify other. Hint: CNG transit buses usually have large fuel tanks mounted on their roof.

FULL TRAILER - a full trailer is a trailer with axles in the front as well as the rear. It can stand without support. Full trailers are coupled to straight trucks and to the rear of semi or full trailers by a tongue or drawbar. Full trailers are seldom used alone with tractors.


GARBAGE/REFUSE - a cargo body style typified by Garbage trucks that often have hydraulic packing mechanisms or hydraulic arms for lifting dumpsters. Included are roll-offs, vehicles used for transporting refuse containers. Roll-offs have rails or a flat bed and a hoist for loading and unloading the refuse container.

GASES IN BULK - these are carried in pressurized tankers only, and are not otherwise containerized. Examples: Aerosol propellant, butane, CO2, LPG, nitrogen, and propane.


GENERAL FREIGHT - this cargo category is for processed items, packaged or in some way containerized, and fairly closely packed.

GIN - can refer to cotton, cotton waste, or the engine that separates the cotton from the seed.

GLIDER KIT - usually a cab and chassis without an engine or rear axles. Used to rebuild a wrecked tractor or to custom build to buyer specification.

GONDOLA - refers to coal hopper bottom trailers or large produce bins that are transported on flatbeds.

GOOSENECK - a hitch resembling the neck of a goose. Can be 5th wheel or an inverted ball hitch attachment. Both straight trucks and tractor-trailer rigs can use goosenecks.

GRAVEL TRAILER - a dump trailer or a gravel hopper bottom which is used to haul gravel.

GRAVEL TRUCK - a dump or a hopper bottom truck which hauls gravel.

GROSS VEHICLE WEIGHT RATING - the vehicle weight plus MAXIMUM CARGO WEIGHT. The GVWR is NOT the unloaded weight.


HEADACHE RACK - a heavy bulkhead that is positioned behind the cab of a power unit. Usually made of pipe and meant to stop any forward cargo shift. See BULKHEAD.

HEAD RAMP - an apparatus attached over the cab of tractors to carry motor vehicles as freight. Auto carriers may or may not have HEAD RAMPS.

HEAVY MACHINERY - this cargo category will tend to be on flatbed trucks and trailers, though not necessarily. Examples: Off road-vehicles, like bulldozers and backhoes, forklifts, construction machinery, large lathes, and farm tractors.

HIGH PLATFORM BUS - depicting heavy-duty, OTR (over-the-road) coaches and tour buses designed for long-distance or intercity travel. Passenger platform higher than driver's seat, with large cargo holds under floor. May have lavatory. Some are two axle vehicles but most are found with three axles - one steering, one four-wheeled drive and one two-wheeled tag axle.

HOIST - sometimes used to refer to the lifting mechanism under cargo bodies that dump.

HOPPER BOTTOM - an open top cargo body capable of discharging its load through a bottom opening without tilting. Sometimes referred to as bottom dumps.

HOT SHOT - (Slang) - 1) a local freight hauler; 2) a one ton truck equipped with a fifth wheel for pulling light weight trailers.

HOUSEHOLD GOODS - this cargo category is for uncrated household or office furniture, band equipment, theatrical equipment, and trade show displays.


ICC - (Interstate Commerce Commission). The federal body formerly charged with enforcing Acts of Congress affecting interstate commerce. The ICC was decommissioned in 1993.

ICC BUMPER - typically made out of 3" to 4"steel channel stock, usually about 75% of the width of the trailer, suspended half the distance from the trailer floor to the pavement with a strong enough bracing to meet federal regulations governing underride guards.

INSULATED TRAILER - a trailer designed for transporting commodities at controlled temperatures, usually provided with refrigerating and/or heating equipment.

INTERCITY BUS - any bus providing long-distance passenger transportation between cities over fixed routes with regular schedules.

INTERMODAL CONTAINER - a cargo container designed for high-speed transfer of cargos between different transportation modes. Typically seen around harbor ports, railway yards, and cargo storage facilities.

INTERSTATE - trucking commerce crossing state lines.

INTRASTATE - trucking commerce within the same state.


JACKKNIFE - skidding of an articulated vehicle sometimes results in rotation at the articulation (hitch) point so that the tractor is rotated against the trailer in a manner similar to the closing of a jackknife.

JAKE BRAKE - a device that increases braking efficiency by manipulating the engine valves to create engine drag, also referred to as an engine retarder.

JEEP DOLLY - a heavy-duty goose neck dolly usually with 2 or more axles that support the front of a cradle frame for transporting large objects or a heavy-duty lowboy trailer.


KINGPIN - attaching pin on a semitrailer that attaches to and pivots within the fifth wheel of a tractor or converter dolly.


LCV - (Longer Combination Vehicle) - a tractor pulling two or more semitrailers on an interstate roadway weighing more than 80,000 lbs., or a doubles rig with either trailer greater than 28.5 feet in length.

LEASE - truck companies sometimes lease trucks or trailers from leasing companies. For our purposes a long-term lease is equivalent to ownership, and the lessee is the operating authority.

LICENSED WEIGHT - the maximum gross weight (vehicle plus cargo) a vehicle is licensed to carry.

LIFT OFF CONTAINER - a cargo container that is loaded and unloaded with a crane, most cargo containers are of this type, the exceptions are roll-offs and the air freight container.

LIQUIDS IN BULK - this cargo category describes the contents of liquid tanks that are not otherwise packaged. Examples include brine, gasoline, whiskey mash, milk, driller's mud (90% water), oil, septic waste, molten sulfur, sulfuric acid, water, tallow, live fish if transported in water.

LIVESTOCK CARRIER - this trailer cargo body style typically has slotted or slatted sides. It may have a double deck. These trailers sometimes have "possum bellies," compartments in the bottom for holding smaller animals.

LIVESTOCK BODY - truck or trailer designed for the transportation of farm animals. Sometimes have double decks. Often has slatted or perforated sides.

LOADER- (1) an off road vehicle with a large 'bucket' or shovel on the front to move material, particularly dirt or debris. (2) refers to a hydraulic mechanism mounted on a trailer or behind the cab of a truck or tractor used to load cargo onto the trailer or truck. Some logging industry trucks are equipped with log loaders for loading fresh cut logs. See FRONT-END LOADER

LOG BOOK - a daily record of a driver's hours, routes, etc. Required by the Department of Transportation.

LOGGING TRAILERS - some pole trailers consist of a set of axles with a cradle to hold logs and a pole attached to the rear of a power unit. Others are skeletally framed. Some have double decks. Most will have cradle-like features called BUNKS to hold the logs in place.

LOGS, POLES, LUMBER - this cargo category includes processed wood, like 2x4's, plywood, pulpwood, firewood, and new pallets, fresh from the factory, but not used empty crates. Wood chips, wood residuals, and bark are solids in bulk.

LOW BOY - gooseneck flatbeds slung very low to the ground. Often the gooseneck is detachable so that equipment can be loaded from the front. Sometimes ramps are at the rear. Typically about 12" off the ground.

LTL - (Less Than (truck) Load). refers to situations in which general freight from various shippers is combined into a truck load.(See FAK)


METAL - this cargo category is for processed, generally unpackaged, metal only. This category includes metal pipe, coils, metal fencing, ingots, steel plates, corrugated tin, and similar processed metal cargoes. This category includes items like steel guard rails, and other manufactured metal items that do not fall in either the heavy machinery, large object, or general freight categories.

MOTOR VEHICLES - this cargo category refers to motor vehicles capable of at least 40 MPH on-highway, carried such that no wheels touch the road. These will probably be on flatbed trucks and trailers or on auto-carriers.

MICHIGAN DOUBLES - a combination vehicle consisting of a tractor pulling two trailers with a total of 11 axles, typically for hauling gravel(dump trailers) or steel (flatbed trailers).


NECK - refers to the nonload bearing coupling portion of a trailer.

NET - in weighing terminology, refers to cargo weight. (Tare = unloaded, Net = cargo, Gross = Tare + Net).

NHTSA - (National Highway Traffic Safety Administration). part of the U.S. Department of Transportation.


OCEAN CONTAINER - a completely enclosed, often water tight container designed to be loaded onto ocean freighters to carry commodities overseas.

OILFIELD BODY - heavily constructed platform-type body equipped with instruments and machinery for oil drilling.

OMC - (Office of Motor Carriers). interstate heavy truck and bus regulatory agency.

OPEN TOP VAN - a cargo body style with sides but without a permanent top.

OPERATING AUTHORITY - the entity responsible for a truck being on the roadway. An example would be if you own the truck and are transporting your own cargo then you would be the operating authority; or if you needed a commodity shipped and hired a trucking company to transport it for you, then the trucking company would be the operating authority. A rule of thumb in determining operating authority is to examine who owns or is responsible for the cargo.

OUTRIGGER - leg-like extensions used on the front or rear of machinery to improve stability. Also, structural load-carrying members attached to and extending from the main frame of a trailer.

OVER-THE-ROAD - Travel from one city to another, as distinct from travel in and around the vehicle's base.

OWNER-OPERATOR - A for-hire carrier who both owns and drives a vehicle and serves as the operating authority.


PIGGYBACK - refers to the way empty log trailers are carried on the bed of a tractor such that no axles touch the ground. Also may refer to other kinds of vehicles carried on the rear of a power unit in a manner that axles do touch the road. See also DECK SET.

PIGGYBACK/TOWAWAY - this cargo category refers to motor vehicles being carried piggyback on a power unit. The trucks being carried have their front axles off the ground resting on the vehicle in front. Several vehicles may be hitched together in this way. This category is also used for wreckers towing a vehicle. Piggyback also refers to the way empty log trailers are carried on the bed of a tractor such that no axles touch the ground. Also may refer to other kinds of vehicles carried on the rear of a power unit in a manner that axles do touch the road. See also DECK SET.

PLATFORM TRAILERS - normally flatbed trailers. There are straight platforms, single drops and double drops.

POLE TRAILERS - a logging trailer. Usually has bunks for holding logs. The center portion of the trailer may be adjustable in order to accommodate loads of different lengths.

POLE TRUCK - (1) also, WINCH TRUCK - it has lifting equipment for lifting poles in oilfield service and contracting. It can have an A-frame. (2) Sometimes refers to a flatbed with bunks.

PONY AXLE - (Slang) for a smaller diameter wheel attached to a lift axle.

POSSUM BELLY TRAILER - a livestock trailer.

POTATO TRUCK OR TRAILER - a hopper bottom or a live bed truck used to carry potatoes. A "spud bed."

POWER UNIT - a truck, or the part of a combination that has the engine.

PRIVATE CARRIER - a company which maintains its own trucks to transport its own freight.

PSC (or PUC) - Public Service Commission (or Public Utilities Commission) - the state body which regulates utilities and for-hire trucking operations within a state's boundaries.

PTO - (Power Take Off) - an outlet from a vehicle engine used to transfer power to towed equipment or machinery.

P/U, PU, PK - common abbreviations for pickup truck.

PULL TRAILERS - a full trailer. It has at least two axles, and will attach with either a ball or a pintle hitch. See PUP TRAILER.

PULPWOOD - logs (usually shorter and smaller in diameter) used for making pulp to manufacture paper.

PUP TRAILER - a short semitrailer used in combination with a dolly and another semitrailer to create a twin trailer. Sometimes used to refer to a short semitrailer not in twin combination. Sometimes a pull trailer is referred to as pup. See PULL TRAILER.

PUSHER AXLE - powered rear axle on a vehicle having a nonpowered axle ahead of it.



RACKS - removable wood or metal wall sections attachable to flatbed trailers to make sides for confining loads.

RAILWAY CONTAINER - a cargo container that can be loaded or stacked on a railroad flat car.

REAR LOADER - a refuse truck that is loaded at the rear usually with some kind of compacting mechanism.

REEFER - (Slang) a van style cargo body with a refrigeration unit.

REFRIGERATED FOODS - this cargo category is for cargoes carried in refrigerated cargo bodies. Ice is included in this category.

REFRIGERATED VAN -a cargo body style typified by a totally enclosed box with a refrigeration unit.

REFUSE - a cargo body style synonymous with garbage trucks that often have hydraulic packing mechanisms or hydraulic arms for lifting dumpsters. Included are roll-offs, vehicles used for transporting refuse containers. Roll-off refuse trucks have rails or a flat bed and a hoist for loading and unloading the refuse container.

REFUSE BODY - a cargo body designed for loading and hauling rubbish.

ROCKY MOUNTAIN DOUBLES - a combination vehicle consisting of a tractor pulling a 45 to 48 foot semitrailer and second shorter semiteailer (usually 28 feet in length).

ROLL-OFF CONTAINER - typically an open top container designed for transporting solids in bulk, often used as REFUSE CONTAINERS. The vehicles used for transporting roll-off containers have rails or a flat bed with a hydraulic hoist for loading and unloading these large containers.


SCHOOL BUS - any bus contracted by any public or private school or school district to provide transportation to its pupils.

SCISSORS DUMP - a dump truck with a special hydraulic system.

SCISSORS LIFT - a cargo body which is used to lift materials to a higher surface, such as lifting shingles to a roof.

SEMITRAILER - the front portion of a semitrailer rests on the back of a tractor. The semitrailer is coupled to the tractor by the fifth wheel on the tractor and the kingpin on the trailer. A semitrailer has no front axle and cannot stand without support. Semitrailers are pulled by tractors only. A trailer whose front half rests on the back of a tractor, coupled to the tractor by a fifth wheel.

SIDE LOADER - a refuse truck which is loaded from the side.

SINGLE DROP TRAILER - a type of flatbed trailer. The rear is closer to the ground than the front. Also called SINGLE DROP PLATFORM.

SLIDING FIFTH WHEEL - a fifth-wheel assembly capable of being moved forward or backward on the tractor to adjust the load distribution on the tractor and the overall length of the rig.

SMALL COWL AND CHASSIS BUS TYPE - depicted by light-duty, non school bus shuttle coaches utilizing a van or RV cutaway chassis.

SOLIDS IN BULK - this cargo category is for commodities that are not packaged, and are generally carried loose.

SPREAD AXLE - tandem trailer axle assemblies spaced further apart than the standard spacing. State and federal bridge laws favor trailer axles with a wider spread by allowing higher weight than on tandems with standard spacing.

SPREAD TANDEM - a two-axle assembly with the axles spaced to allow maximum axle loads permitted by existing regulations. Distance between centers of axles of a spread tandem has generally been over 50 inches.

STAKE BODY - a flatbed with sides or stakes to retain the load.

STEERABLE DOLLY - used in transporting extremely long objects, some can be steered remotely from the cab.

STEERING AXLE - an axle through which directional control of the vehicle is applied. It may be powered or not and there may be more than one steering axle on a single unit.

STEP BUMPER - a bumper that can also function as a stepping platform either into or out of a cargo body, usually these bumpers are mounted relatively close to the ground.

STEP VAN - a lightweight delivery truck designed so the driver can step into and out of the cab as well as into the rear cargo area.

STINGER FIFTH WHEEL - seen most commonly as the connection point for auto-carriers, but are also seen on some logging rigs. The inverted fifth wheel is mounted behind the rear axles, at the very end of the tractor, less than a foot off the ground.

STRAIGHT TRUCK - this is a one unit vehicle capable of carrying cargo. Examples include refuse, tank, and dump trucks. Straight trucks may or may not pull trailers.



TAG or TAGALONG TRAILERS - usually single axle equipment like generators, cement mixers, or wood chippers.

TAG AXLE - a nondrive rear axle on a truck or tractor.

TANDEM AXLE - refers to a pair of axles at the rear of the power unit (tractor or straight truck) or trailer. For power units, if described as a tandem, usually indicates the number of drive axles on the power unit.

TANKER - an enclosed cargo body designed solely for the transportation of fluid or gaseous commodities in bulk. Not to be confused with trailers which are designed for carrying dry bulk products.

TANKER - DRY BULK - sometimes called air-can trailers. Used exclusively for hauling dry bulk material. Cargo is emptied pneumatically.

TANK - LIQUID/GAS - a cargo body style characterized by tankers which can carry only liquids or gases in bulk.

TARE WEIGHT - the weight of a vehicle without a load. See also NET.

TILT - a cab which tilts up for maintenance. It does NOT mean the vehicle is necessarily COE. The engine cowls of some conventional power units tilt although the entire cab does not.

TILT BODY - a flatbed for hauling equipment. Sometimes specialized dumps are called this.

TIPPER - rear/side tipper - specialized dump rig, usually. A roll-off tipper is a roll-off container carrying setup.

TOTER - a power unit designed to transport mobile homes.

TRACTOR - a tractor is a vehicle designed to pull semitrailers and generally has no cargo capacity. It is used for pulling semitrailers only. Unlike the straight truck which has a cargo body mounted to the truck frame, the tractor has a circular fifth wheel plate for coupling to a semitrailer. This category includes gooseneck hitch tractors, even though they lack fifth wheels. This category includes auto carrier tractors with racks for carrying automobiles. This category also includes mobile home haulers described as tractors. (That is, with fifth wheels and/or ball hitches and lacking cargo bodies.) Tractors can carry motor vehicles in a saddlemount or piggyback fashion.

TRANSFER DUMP - a common configuration in California; typified by a straight dump truck pulling a full dump trailer without hydraulics. The dump box of the trailer slides (transfers) into the empty dump bed of the power unit utilizing the hydraulics of the power unit to unload.

TRANSIT BUS - a bus providing passenger transportation over fixed scheduled routes within primarily urban geographical areas.

TRI-AXLE - normally implies four total axles if used to refer to a straight truck.

TUBE TRAILER - a semitrailer used to transport cryogenic gases.

TURNPIKE DOUBLES - a combination vehicle consisting of a tractor and two 40 to 53 foot trailers.

TURNTABLE - a circular platform mounted under the front of a full trailer or a jeep dolly to which an axle or axles are attached, allowing the axles to pivot in a turning maneuver.

TWIN SCREW - a truck or tractor with two rear axles, both driven by the engine.


TYPE A SCHOOL BUS - depicting a van conversion or bus constructed utilizing a small cowl and chassis, van-based cutaway. Has a nose and grille like a typical van, a regular driver's door (on the left side of vehicle), and the passenger entrance door curbside, behind the front wheel. Front engine location.

TYPE B SCHOOL BUS - depicting a school bus constructed on a stripped van or truck chassis, perhaps resembling a step-van type of front. Full coach body, with only one door, curbside, behind the front wheels. Front engine location.

TYPE C SCHOOL BUS - depicting a conventional school bus consisting of a coach body mounted on a truck-based, flat back cowl (big cowl and chassis - hood and fender assembly). Varying lengths and some have wheelchair lifts. There is typically one entrance door located behind the front wheels. Front engine location.

TYPE D SCHOOL BUS - depicting a transit-style school bus. Flat front, full coach body mounted on stripped bus chassis. Can be either front (forward control, FE) or rear engine (RE). Varying lengths, can have wheelchair lift and small storage compartments under passenger floor (accessed though small hatch doors on side of bus).


UNDERRIDE - occurs primarily in rear-end collisions when the striking vehicle is wedges under the rear of the vehicle being struck.

UNDERRIDE GUARD - a rear impact guard installed at the rear or under the rear of the cargo body of a truck or trailer so that when the vehicle is struck from the rear, it can limit the distance that the striking vehicle's front end slides under the rear of the truck or trailer. Most semitrailers have what are known as ICC bumpers, but a hydraulic liftgate at the rear of a box van can act as an underride guard. See ICC BUMPER.

UTILITY TRAILER - normally refers to light duty trailers, esp. flatbeds. UTILITY is also the name of a trailer manufacturer.


VAN - a cargo body style with a totally enclosed cargo area. Included are beverage vans, or bay vans, and sealed shipping containers mounted on a special bodiless chassis.


WALKING FLOOR - also known as a "live bottom", a type of dump trailer with a conveyor belt or chain running down the center of the floor of the trailer to unload the cargo.

WHEELBASE - for a straight truck or a truck tractor, the distance from center of front axle to center of rear axle, for a two axle vehicle, or front axle center to the midpoint between the rear tandem axle centers for a three axle vehicle. For a truck tractor and semitrailer combination, wheelbase refers to from the center of the front tractor axle to the center of the rearmost trailer axle.

WINCH TRUCK - a winch is a powered spool wound with cable. Winches are used to lift or to pull heavy objects. Winches vary in size from those on the front of small vehicles to heavy equipment which may weigh tons.

WRECKER - a truck designed for hoisting and towing disabled vehicles.



YARD HORSE - a tractor for moving trailers short distances in a truck yard or terminal compound. Also called SWITCHING TRACTOR, YARD TRACTOR, TRAILER SPOTTER, YARD DOG, and LINEHAULER. Equipment is manufactured and sold for such exclusively off-road use, but sometimes old, spare, or unroadworthy tractors are used.