Glossary of Trucking Terms

A list of common trucking terms and definitions commonly used in the freight, transportation, and trucking industries in the United States.

‘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.

ABS (Antilock Braking System): Computer, sensors and solenoid valves which together monitor wheel speed and modulate braking force if wheel lockup is sensed during braking. Helps the driver retain control of the vehicle during heavy braking on slippery roads.

AFV (Alternative Fueled Vehicle):  Vehicle powered by a fuel other than gasoline or diesel.

Air Ride Suspension: 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.

APU: Auxiliary power units allow truck drivers to have climate control for their sleepers and electricity for hotel loads without needing to idle the tractor engine. tAPUs can be powered by a small diesel engine or by batteries.

ATA – American Trucking Associations. This industry trade association, headquartered in Virginia, is the umbrella organization for 50 affiliated state trucking associations.

ATC (Automatic Traction Control): Usually an optional feature based on ABS, it prevents spinning of the drive wheels under power on slippery surfaces by braking individual wheels and/or reducing engine throttle. Also called ASR, an acronym sometimes loosely translated from the German as anti-spin regulation.

Authority – In order to operate legally, both for-hire carriers and freight brokers must obtain operating authority from the U.S. Department of Transportation (DOT).

AVI (Automatic Vehicle Identification): System combining an on-board transponder with roadside receivers to automate identification of vehicles. Uses include electronic toll collection and stolen vehicle detection. (see IVHS)

AVL (Automated Vehicle Location): Class of technologies designed to locate vehicles for fleet management purposes and for stolen vehicle recovery. Infrastructure can be land-based radio towers or satellites. (see IVHS)

Axle: Structural component to which wheels, brakes and suspension are attached.

  • Drive axles are those with powered wheels.
  • Front axle is usually called the steer axle.
  • Pusher axles are unpowered and go ahead of drive axles.
  • Rear axles may be drive, tag or pusher types.
  • Tag axles are unpowered and go behind drive axles.

Axle Load: The official weight limit for trucks, calculated by distribution over each axle.

‘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.

Back-Haul:  A trip back to the point of origin after delivery, frequently have partial or empty trailers running.

Bay or Dock: Used to describe place in warehouse trailer will be taken, to be loaded/un-loaded.

BBC: Distance from a truck’s front bumper to the back of its cab.

Bill of Lading (BOL): Legal document filled out by shipper stating type, weight and quantity of freight. Itemized list of goods contained in a shipment.

Blind Spot: Areas around a commercial vehicle that are not visible to the driver either through the windshield, side windows or mirrors.

Bobtail: Tractor operating without a trailer. Also refers to straight truck.

Bogie (also spelled bogey): Assembly of two or more axles, usually a pair in tandem.

Brake Horsepower (bhp):  Engine horsepower rating as determined by brake dynamometer testing. (see Horsepower)

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 vehicle’s axles, and how far apart the axles (or groups of axles) must be to legally carry a given weight.

Broker: A person with industry experience who negotiates shipping arrangements and rates for an owner-operator or fleet.

Bunk: See Sleeper.

Cabover (Cab-Over-Engine, COE): Truck or tractor design in which the cab sits over the engine on the chassis.

Cargo Weight:  Combined weight of all loads, gear and supplies on a vehicle.

Cartage Company: Company that provides local (within a town, city or municipality) pick-up and delivery.

Cast Spoke Wheel:  Wheel with five or six spokes originating from a center hub. The spoked portion, usually made of cast steel, is bolted to a multiple-piece steel rim (see Demountable Rim; Disc Wheel).

CB (Citizens Band Radio): Two-way radio for which no license is required by the Federal Communications Commission (FCC). Long beyond its heyday in the ’70s, CB is still used by truckers and motorists for everything from traffic condition reports to emergency calls to idle chatter.

CDL (Commercial Driver’s License):  License which authorizes an individual to operate commercial motor vehicles and buses over 26,000 pounds gross vehicle weight. For operators of freight-hauling trucks, the maximum size which may be driven without a CDL is Class 6 (maximum 26,000 pounds gross vehicle weight).

CE (CF, LP): Distance from back of a truck’s cab to the end of its frame.

CFC:  Chlorofluorocarbon.

CG (Center of Gravity): Weight center or balance point of an object, such as a truck body. Calculated to help determine optimum placement of truck bodies on chassis.

Chassis Weight (Curb Weight, Tare Weight): Weight of the empty truck, without occupants or load.

Class A (CDL): Refers to type of commercial driver’s license allowing an individual to drive tractor trailers.

Classification:  Guidelines to assign characteristics to describe freight primarily for billing purposes. (See NMFC)

CNG: Compressed natural gas.

COE: See Cabover.

COFC (Container On Flat Car):  Method of moving shipping containers which involves transporting them on railroad flat cars.

Common Carrier (LTL): A trucking company that will haul freight to anyone. This is different than other companies that only haul to private or dedicated customers.

Compensated Intracorporate Hauling:  Freight transportation service provided by one company for a sister company.

Container (Shipping Container): Standard-sized rectangular box used to transport freight by ship, rail and highway. International shipping containers are 20 or 40 feet long, conform to International Standards Organization (ISO) standards and are designed to fit in ships’ holds. Containers are transported on public roads atop a container chassis towed by a tractor. Domestic containers, up to 53 feet long and of lighter construction, are designed for rail and highway use only.

Container Chassis: Single-purpose semi-trailer designed to carry a shipping container.

Contract Carrier: Company that transports freight under contract with one or a limited number of shippers.

Converter Dolly (Dolly): Auxiliary axle assembly equipped with a fifth wheel (coupling device), towed by a semi-trailer and supporting the front of, and towing, another semi-trailer.

Cube (Cubic Capacity):  Interior volume of a truck body, semi-trailer or trailer, measured in cubic feet.

Curb Weight:  See Chassis Weight.

Day cab: a short tractor which has no sleeper berth. Often for local work where the driver gets home every night.

Dead Axle: Non-powered axle (usually rear) on tandem truck or tractor, often present on commercial vehicles to increase weight-carrying capacity of unit. Also called 6×2.

Deadhead: A back haul with no freight. Deadheading generates no profit and drives up cost per mile.

DEF (Diesel Exhaust Fluid): a liquid used to reduce the amount of air pollution created by a diesel engine. Also see SCR

Demountable Rim: Multi-piece steel wheel rim assembly which is bolted to a spoke hub. Demountable rims are still in use, though they have been replaced in many applications by the simpler disc wheel. (see Cast Spoke Wheel)

Density: Determined by measuring, Length x Width x Height divided by 1728 = cubic feet. Divide the weight by the cubic feet to give the density.

Disc Wheel: Single-piece rim/wheel assembly of stamped and welded steel or forged aluminum, anchored by 8 or 10 nuts to a hub. A “Budd wheel” is a ten-hole, stud-piloted disc wheel; a design originated by the Budd Corporation.

Displacement (Piston Displacement): Sum of the volumes swept by an engine’s pistons as they travel up and down in their cylinders. Based upon bore (diameter of cylinder) and stroke (distance traveled by piston). Expressed in liters or cubic inches.

Dock: See Bay

Dolly: See Converter Dolly.

Double(s) (Twins, Twin Trailers): Combination of a tractor and two semi-trailers connected in tandem by a converter dolly. (see Converter Dolly; Pintle Hook)

DPF (Diesel Particulate Filter) – An exhaust After Treatment system that uses heat to oxidize soot to produce cleaner engine exhaust.

Drayage – Carrying freight a short distance as part of a longer trip. For example, a tractor picking up freight from a rail yard and carrying it 50 miles to its final destination.

Driveline: All the components which together transmit power from the transmission to the drive axle(s). These consist of at least one driveshaft (propeller shaft) with a universal joint at each end.

Drivetrain (Powertrain): All the components, excluding engine, which transmit the engine’s power to the rear wheels: clutch, transmission, driveline and drive axle(s). (See Powertrain)

DRL (Daytime Running Lights): System that automatically turns on a vehicle’s low beam headlights when the parking brake is released and the ignition is on.

EDI (Electronic Data Interchange): The business-to-business interconnection of computers for the rapid exchange of a wide variety of documents, from bills of lading to build tickets at auto plants.

E-Log: A computer system that keeps track of a truck driver’s miles and service. When using an E-log, carries will have instant access to their driver’s logs. This allows carriers to improve scheduling drivers

ELD (Electronic Logging Device): An on-board device that records information about the movement of a truck, including speed and time in service, as well as the driver’s hours of service and duty status. As of December 2017, ELDs are required on all trucks (with some exceptions), replacing paper logs kept by drivers. Trucks that were previously equipped with AOBRDs were permitted to continue using those devices until December 16, 2019, when they must switch to ELDs, as well.

EOBR (Electric On-Board Recorder) – Cab-mounted device which electronically records data such as truck speed, engine rpm, idle time and other information useful to trucking management

Escape Ramp: See Runaway Truck Ramp.

EV (Electric Vehicle): Vehicle powered by electric motor(s) rather than by an internal combustion engine. Most common source of electricity is chemical storage batteries.

Exempt Carrier: Company which transports commodities exempted from Interstate Commerce Commission (ICC) economic regulation.

Expedite freight – Time-sensitive freight that must be delivered at a pre-set delivery time.

Factoring – In the trucking industry, factoring is when a carrier receives payment from a third-party financial company before delivering a load and waiting for payment, thereby improving cash flow. The factoring company retains a fee, typically based on a percentage of what the carrier would have earned. Freight brokers may also rely on factoring to improve cash flow.

FAK: (Freight All Kinds):  Specialized rates where several similar commodities may fall under one classification. Usually only given to very high-volume customers.

Fifth Wheel: Coupling device attached to a tractor or dolly which supports the front of a semi-trailer and locks it to the tractor or dolly. The fifth wheel’s center is designed to accept a trailer’s kingpin, around which the trailer and tractor or dolly pivot in turns.

Fixed Tandem: Assembly of two axles and suspension that is attached to the chassis in one place, and cannot be moved fore and aft. (see Sliding Tandem)

Flatbed – An open trailer used for carrying construction materials and equipment and other objects of unusual size and shape.

FMCSA (Federal Motor Carrier Safety Administration): Government agency responsible for regulating the US commercial trucking industry

For-Hire Carrier:  Company in the business of transporting freight belonging to others (see Private Carrier).

Forced Dispatch – When the company dispatcher assigns a load, customer and delivery time to a driver and the driver must take the load or suffer consequences (such as being forced to wait around several hours or another day for another load, or even being fired).

Freight Broker: A person or organization you contact to make shipping arrangements for you. They will add charges over what they pay and bill you.

Freight Forwarder: Similar to a freight broker but generally specialize in over-seas and/or air freight. They consolidate many individual shipments together for shipping in a single container and arrange delivery upon arrival at destination port. They are also specialists in customs paperwork and duties.

GAWR (Gross Axle Weight Rating): 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): Total weight of a loaded combination vehicle, such as a tractor-semi-trailer or truck and full trailer(s).

Gear Ratio: Number, usually expressed as a decimal fraction, representing how many turns of the input shaft cause exactly one revolution of the output shaft. Applies to transmissions, power takeoffs, power dividers and rear axles. Example: If 2.5 revolutions of an input shaft cause one revolution of the output shaft, the gear ratio is 2.5:1.

Geared Speed: Calculated vehicle speed at the engine’s governed rpm in each transmission gear, or (commonly) in top gear.

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.

Governor – A device that regulates the truck’s top speed. Large fleets use these to ensure their drivers stay within guidelines to improve fuel efficiency and safety.

Grade:  Steepness of a grade, expressed as a percentage. Example: A vehicle climbing a 5% grade rises 5 feet for every 100 feet of forward travel.

Gradeability: Vehicle’s ability to climb a grade at a given speed. Example: A truck with a gradeability of 5% at 60 mph can maintain 60 mph on a grade with a rise of 5%.

GVW (Gross Vehicle Weight):  Total weight of a vehicle and everything aboard, including its load.

GVWR (Gross Vehicle Weight Rating): Total weight a vehicle is rated to carry by the manufacturer, including its own weight and the weight of its load.

Hazmat: Hazardous materials, as classified by the U.S. Environmental Protection Agency (EPA). Transport of hazardous materials is strictly regulated by the U.S. Department of Transportation.

HCFC:  Hydrochlorofluorocarbon.

Headache Rack:  Heavy protective barrier mounted behind the tractor’s cab. Designed to prevent “headaches” caused by load shifting forward from the trailer and crushing the cab.

Head-Haul: A lane that regularly has trailers running full or at capacity.

Horsepower (hp): Measure of power (the amount of work that can be done over a given amount of time). One horsepower is defined as 33,000 foot-pounds of work in one minute. Example: Lifting 33,000 pounds one foot in one minute, or lifting 3300 pounds ten feet in one minute.

Horsepower, Gross Laboratory:  Tested horsepower of a “bare” engine without fan, water pump, alternator, exhaust system or any other accessories.

Horsepower, SAE Net: Horsepower capability of an engine with full accessories and exhaust system. Test procedures per standards of Society of Automotive Engineers (SAE).

Hours-Of-Service (HOS):  U.S. Department of Transportation safety regulations which govern the hours of service of commercial vehicle drivers engaged in interstate trucking operations.

Hot shot – Expedited freight normally limited to a gross weight of 36,000 pounds. Can also refer to the truck hauling the freight, which can be as small as a one-ton pickup hauling a flatbed trailer.

Hub:  A large terminal where freight from regional terminals is organized for transit.

IFTA – International Fuel Tax Agreement. An agreement between the lower 48 United States and Canadian provinces, in which carriers report fuel tax paid at the pump on a quarterly basis, and the money is redistributed to the states and provinces where the fuel was used.

Independent Trucker: See Owner Operator.

Inside delivery: Charges assessed by a trucking company for delivery within an establishment or home. Charges are in addition to normal freight charges. Appointment many be needed as well as liftgate delivery.

Inspector: Person from independent company who will evaluate freight for damage and estimate loss.

Interline: Term used when freight is given to smaller usually rural regional carriers.

Intermediary – In trucking, this term usually refers to a freight broker or third-party logistics (3PL) company that manages transportation on behalf of a shipper.

Intermodal Transportation –The transportation movement involving more than one mode (e.g., rail/motor, motor/air, rail/water).

Inter-state: Freight originating in one state, going to another.

Intra-state: Freight whose origin and destination are within the same state.

ITS (Intelligent Transportation Systems): See IVHS.

IVHS (Intelligent Vehicle Highway Systems): Blanket term for a wide array of technologies, including electronic sensors, computer hardware and software and radio communications. The purpose of IVHS is to increase efficiency of use of existing highways, reducing travel time, fuel consumption, air pollution and accidents. There are five functional areas:

  • Advanced Public Transportation Systems (APTS)
  • Advance Traffic Management Systems (ATMS)
  • Advance Traveler Information Systems (ATIS)
  • Advanced Vehicle Control Systems (AVCS)
  • Commercial Vehicle Operations (CVO)

A more recently coined term, Intelligent Transportation Systems (ITS), encompasses both IVHS and modes of transportation other than highway, such as rail. (see AVI, AVL, WIM)

Jackknife: To place the trailer at a very sharp angle to the tractor.

Jake Brake: See Retarder.

JIT (Just-In-Time): Manufacturing system which depends on frequent, small deliveries of parts and supplies to keep on-site inventory to a minimum.

Kingpin (axle): Pin around which a steer axle’s wheels pivot.

Kingpin (trailer): 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.

Landing Gear: Retracting legs which support the front of a semi-trailer when it is not coupled to a tractor.

Lane: Specific routes trucks are dispatched (usually on daily basis).

LCV (Long Combination Vehicle): In general, vehicles 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.

Lessee: Company or individual which leases vehicles.

Lessor: Company which leases vehicles.

Lift Axle: Extra, unpowered axle needed only when the vehicle is loaded, allowing it to meet federal and state vehicle weight standards. The lift axle is mounted to an air spring suspension that raises the axle when it is not required.

Liftgate: The use of a special truck which can load, un-load without a loading dock. An attached movable ramp can be lowered from trailer to raise heavy items or fork lift. Additional charges usually apply. Appointment usually needed.

Line-Haul: The group within the carrier responsible for proper allocation of equipment throughout service area.

Line-haul Driver –Truck driver who travels a set route from city to city and typically returns home after each shift. Also known as a regional driver.

Local Driver –Truck driver who picks up and delivers packages along a city route. Drivers typically run the same route every day, returning home after each shift. Also known as a city or P&D driver.

Load – A single freight shipment.

Load board – A service that matches shippers and freight brokers with carriers (trucking companies) willing to transport the freight. DAT (originally called Dial-A-Truck) created the first electronic load board in 1978 at Jubitz Truck Stop in Portland, Oregon, replacing the previous system of index cards pinned to bulletin boards.

Load-to-truck-ratio – The number of trucks available for hire in a specific location versus the number of available loads at that location. A high load-to-truck ratio in a certain city, state, or region means that a carrier is more likely to find freight there.

Load Range (Tires): Letter code system for the weight carrying capacity of tires. Comparable ply ratings are shown below. (LR = Load Range PR = Ply Rating)

LR      PR      

A         2

B         4

C         6

D         8

LR      PR

E          10

F          12

G         14

H         16

Logbook: Book carried by truck drivers in which they record their hours of service and duty status for each 24-hour period. Required in interstate commercial trucking by the U.S. Department of Transportation.

Lowboy: Open flat-bed trailer with a deck height very low to the ground, used to haul construction equipment or bulky or heavy loads.

LPG: Liquid propane gas.

LTL (Less-Than-Truckload): A quantity of freight less than that required for the application of a truckload (TL) rate; usually less than 10,000 pounds. (see TL)

LTL Carrier: Trucking company which consolidates less-than-truckload cargo for multiple destinations on one vehicle. (see TL Carrier).

NMFC: National Motor Freight Classification, assigned independently by the NMFTA.

On-Board Computer: See Trip Recorder.

OOIDA (Owner-Operator Independent Drivers Association): An international trade association representing the interests of independent owner-operators and professional drivers on all issues that affect truckers.

Overdrive: Gearing in which less than one revolution of a transmission’s input shaft causes one turn of the output shaft. The purpose of overdrive is to reduce engine rpm in high gear for better fuel economy. Example: A transmission with an overdrive top gear has a ratio of 0.70 to one. Turning the input shaft 0.7 revolutions causes 1.0 revolution of the output shaft.

Owner-Operator: Trucker who owns and operates his own truck(s).

OTR – Over-the-Road. Long-haul trucking, as opposed to local or regional.

P&D: Pickup and delivery.

Payload: Weight of the cargo being hauled.

Peddle: Run Truck route with frequent delivery stops.

Piggyback: Semi-trailer built with reinforcements to withstand transport by a railroad flatcar. (see TOFC)

Pigtail: Cable used to transmit electrical power from the tractor to the trailer. So named because it is coiled like a pig’s tail.

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.

Piston Displacement: See Displacement.

Ply Rating (PR): Relative measure of tire casing strength. (see Load Range)

Powertrain: See Drivetrain.

Private Carrier: Business which operates trucks primarily for the purpose of transporting its own products and raw materials. The principle business activity of a private carrier is not transportation. (see For-Hire Carrier)

Pro:  Tracking number assigned to freight.

PSI (Pounds Per Square Inch): In trucking, unit of measurement for tire air pressure, air brake system pressure and turbocharger boost.

PTDI – Professional Truck Driver Institute. This organization certifies truck driver training programs. It does not teach CDL classes.

PTO (Power Takeoff): Device used to transmit engine power to auxiliary equipment. A PTO often drives a hydraulic pump, which can power a dump body, concrete mixer or refuse packer. Some designs mount to a standard opening on the transmission, while others attach at the front or rear of the engine.

Pull Trailer:  Short, full trailer (supported by axles front and rear) with an extended tongue.

Pup Trailer: Short semi-trailer, usually between 26 and 32 feet long, with a single axle.

Pup:  Term used for 28-foot trailers. Typically used by LTL carriers.

Pusher Axle:  See Axle.

Qualcomm: Carriers use a wireless communication that uses GPS, text messaging and email. A Qualcomm allows the trucking company keep track of their drivers along with the status of deliveries and weather.

Rail:  The use of freight trains to move goods.

Reefer: Refrigerated trailer with insulated walls and a self-powered refrigeration unit. Most commonly used for transporting food.

Regeneration: An oxidation process that uses heat to remove the soot from the DPF filter. There are various kinds of Regen: Active, Passive, Automatic and Parked.

Relay (Relay Driving): Common practice in the less-than-truckload industry, in which one driver takes a truck for 8 to 10 hours, then turns the truck over to another driver, pony express style.

Release Value:  The maximum a carrier will pay on a claim per pound for a certain classification or commodity.

Retarder:  Device used to assist brakes in slowing the vehicle. The most common type of retarder on over-the-road trucks manipulates the engine’s valves to create engine drag. (This type is commonly referred to as “Jake Brake” because the predominant manufacturer is Jacobs Vehicle Equipment Co.) Other types of retarders include exhaust retarders, transmission-mounted hydraulic retarders and axle-mounted electromagnetic retarders.

RFG (Reformulated Gasoline): Gasoline blended with pollution reducing additives.

RoadRailer: Semi-trailer specially designed to travel both on highway and on rails. Manufactured by Wabash Corp.

Rolling Radius:  Tire dimension from center of the axle to the ground; measured with tire loaded to rated capacity. Used in calculating geared speed.

RPM (Revolutions Per Minute): Measure of the speed at which a shaft spins. Most often used to describe engine crankshaft speed. Indicated by a tachometer.

Runaway Truck Ramp:  Emergency area adjacent to a steep downgrade that a heavy truck can steer into after losing braking power. Usually two or three lanes wide and several hundred feet long, the ramp is a soft, gravel-filled pathway which absorbs the truck’s forward momentum, bringing it to a safe stop. Depending on the surrounding terrain, the ramp may be level or run up or down hill.

SCR (Selective Catalytic Reduction): technology that injects urea – a liquid-reductant agent – through a catalyst

into the exhaust stream of a diesel engine transforming harmful NOx emissions into harmless exhaust gas.

Semi-trailer: Truck trailer supported at the rear by its own wheels and at the front by a fifth wheel mounted to a tractor or dolly.

Set: (See Double)

Setback Axle: Front steering axle moved rearward from the generally accepted standard position. Advantages: Shorter turning radius and more of a vehicle’s weight shifted to front axle.

Shipping Weight: “Dry” weight of a truck including all standard equipment, but excluding fuel and coolant.

Single-Source Leasing:  Service in which companies can lease drivers and trucks from the same source, rather than having to procure them from different companies.

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

Sleeper Team: See Team.

Sliding Fifth Wheel: Fifth wheel mounted to a mechanism that allows it to be moved back and forth for the purpose of adjusting the distribution of weight on the tractor’s axles. Also provides the capability to vary vehicle combination lengths.

Sliding Tandem (Slider): Mechanism that allows a tandem axle suspension to be moved back and forth at the rear of a semi-trailer, for the purpose of adjusting the distribution of weight between the axles and fifth wheel.

Speedability: Top speed a vehicle can attain as determined by engine power, engine governed speed, gross weight, driveline efficiency, air resistance, grade and load.

Spoke Wheel: See Cast Spoke Wheel.

Spread Axle (Spread Tandem): Tandem axle assembly spaced further apart than the standard spacing of 54 inches. The U.S. federal bridge formula favors trailer axles with an eight- or nine-foot spread by allowing higher weight than on tandems with standard spacing.

Straight Truck: See Truck.

Synchronized Transmission: Transmission with built-in mechanisms to automatically “equalize” the speed of its gears to allow smooth shifting without the need to double-clutch.

Tag Axle:  See Axle.

Tandem Axle (Tandems): Pair of axles and associated suspension usually located close together. (see Spread Axle)

Tare Weight: See Chassis Weight.

Tariff:  A published set of guidelines established by the carrier that designates their legal liabilities.

Team (Driver Team): Team of two drivers who alternative driving and resting.

Terminal Manager:  Person responsible for running a regional dock complex where freight is transferred to other trailers for delivery or transit to other areas.

Terminal:  Regional location where freight is organized for local delivery, transit to other terminals or hubs.

TEU (Twenty-Foot Equivalent Unit):  Standardized unit for measuring container capacity on ships, railcars, etc.

TL (Truckload): The quantity of freight required to fill a trailer; usually more than 10,000 pounds. (see LTL)

TL Carrier (Truck Load): Trucking company which dedicates trailers to a single shipper’s cargo, as opposed to an LTL (Less Than Truckload) carrier which transports the consolidated cargo of several shippers and makes multiple deliveries. (see LTL Carrier)

TOFC (Trailer On Flatcar): Method of moving cargo which involves transporting semi-trailers on railroad flat cars. (see Piggyback)

Top-Freight:  Light weight, usually sturdy freight packed in boxes that can be stacked on top of other fright to fill a trailer.

Tractor Trailer: Tractor and semi-trailer combination.

Tractor: Truck designed primarily to pull a semi-trailer by means of a fifth wheel mounted over the rear axle(s). Sometimes called a truck tractor or highway tractor to differentiate from it from a farm tractor.

Tractor:  The motorized portion of the truck.

Transit Time:  The normal amount of time it takes for freight to go from one point to another. Not generally guaranteed.

Tri-Axle:  Truck, tractor or trailer with three axles grouped together at the rear. (see Tridem)

Tridem: Group of three axles on a truck, tractor or trailer. Tridems are most common on European semi-trailers.

Trip Leasing: Leasing a company’s vehicle to another transportation provider for a single trip.

Trip Recorder (On-Board Computer): Cab-mounted device which electronically or mechanically records data such as truck speed, engine rpm, idle time and other information useful to trucking management.

Triple: Three trailers pulled by one tractor. Illegal in some states.

Truck: Vehicle which carries cargo in a body mounted to its chassis, rather than on a trailer towed by the vehicle.

Twins (Twin Trailers): See Doubles.

ULEV:  Ultra-low emissions vehicle.

Upper Coupler:  Load bearing surface on the underside of the front of a semi-trailer. It rests on the fifth wheel of a tractor or dolly and has a downward-protruding kingpin which is captured by the locking jaws of the fifth wheel.

UTA (Used Truck Association): An impartial organization comprised of used truck professionals and associated businesses committed to strengthening the used truck industry.

VIN (Vehicle Identification Number): Assigned by the manufacturer, this number is unique to each vehicle and appears on the vehicle’s registration and title.

VMRS (Vehicle Maintenance Reporting Standards): Set of codes developed to facilitate computerized tracking of parts and labor used in equipment repair. Established and maintained by the American Trucking Associations.

Walking Beam Suspension: Type of truck and tractor rear suspension consisting of two beams, one at each side of the chassis, which pivot in the center and connect at the front to one axle of a tandem and at the rear to the other axle.

Weigh & Inspection (W&I):  When freight is inspected for misclassification, weight and packaging by a trucking company.

WIM (Weigh-In-Motion): Technology for determining a vehicle’s weight without requiring it to come to a complete stop.

Yard Jockey: Person who operates a yard tractor.

Yard Tractor (Yard Mule, Yard Dog): Special tractor used to move trailers around a terminal, warehouse, distribution center, etc.


Arrow Truck Sales, Inc. strives to provide accurate and reliable information on all it publishes on its website and blogs. Arrow is not responsible for technical inaccuracies and/or typographical errors. Any reliance you place on such material is therefore strictly at your own risk.