Trucking Terminology and Transportation Definitions

Trucking Terminology

A

ABS (Anti-lock Braking System)

Helps the driver retain control under heavy braking.

Air Brake

Brake system operated by air; uses lines, valves, tanks, and a compressor.

Air Ride Suspension

Suspension on air bags instead of steel springs; air supplied by the compressor and reservoirs.

Air Spring System

Pressurized air between container and plunger compresses to create a spring effect.

Air Tank

Reservoir storing compressed air for the brake system.

Axle

Structural member carrying wheels, brakes, and suspension.

• Steer Axle: front axle of the tractor.
• Drive Axles: powered axles.
• Pusher Axles: unpowered; ahead of drives.
• Tag Axles: unpowered; behind drives.
• Rear Axles: may be drive, pusher, or tag.
• Trailer Tandem Axles: usually unpowered; sometimes split for distribution.

B

Back Haul

Return load going back toward the origin instead of running empty.

Balloon Freight

Very light but bulky cargo (cubes out before it weighs out).

Bill of Lading (BOL)

Shipping contract and itemized receipt for the goods in a shipment.

Blind Spot

Areas around a tractor-trailer not visible via windows or mirrors.

Bobtail

Tractor operating without a trailer.

Bogey

Assembly of two or more axles (often a tandem pair).

Bridge Formula

Regulates allowable weight per axle and axle spacing on bridges/roads.

Bulk Freight

Unpackaged commodities (e.g., liquids, grain); hauled in tanks, hoppers, or vans.

C

Cabover

Cab-over-engine tractor design with cab over the engine.

Cartage Company

Motor carrier providing local pickup and delivery.

CAT Scales

Common certified truck-stop scales; guarantee accuracy or cover fines.

CB (Citizens Band Radio)

Two-way radio used by truckers for comms.

CDL (Commercial Driver’s License)

License to operate CMVs/buses over 26,000 lbs GVW.

Check Call

Daily check-in with dispatch (phone/Omnitracs) with progress details.

Clearance Lights (Markers)

Marker lights at trailer corners/top indicating vehicle width/height.

Clutch Brake

Engages with clutch fully depressed; used when stopped to select gear.

Comdata

Issues Comchecks and Comcard for advances and fuel.

• Comcheck: coded paper check for cash advances/expenses.
• Comcard: fuel card; can also receive advances.

Commentary Driving

Training method: trainer/student verbalizes observations and actions while driving.

Container

Standardized box for intermodal freight (20–40 ft ISO; domestic up to 53 ft).

Container Chassis

Trailer specifically designed to carry a container.

Conventional

Tractor with cab behind the engine (vs. cabover).

Converter Dolly

Assembly with fifth wheel that links multiple trailers (doubles/triples).

Consignee

Receiver who accepts the delivery.

Cube

Interior volume capacity of a trailer, in cubic feet.

D

DAC Services

Pre-employment screening used by many carriers.

Day Cab

Tractor with no sleeper; typically local work.

Deadhead

Running without a paying load.

Detention

Extra pay for waiting time at shippers/receivers.

Dock Lock

Device securing the trailer to the dock to prevent movement during loading.

Drop and Hook

Drop a trailer and hook to another; minimizes waiting for load/unload.

Drop Pay

Extra pay for an additional stop/delivery.

Dry Freight

Non-refrigerated freight.

E

Empty Call

Driver notifies dispatch when unloaded and ready for next assignment.

F

Fifth Wheel

Coupling device on tractor/dolly that locks to the trailer’s kingpin.

Fingerprinting

Driver unloading the trailer by hand.

Fixed Tandem

Tandem suspension fixed to the chassis; cannot slide.

Floating the Gears

Shifting without using the clutch.

Freight

The cargo/load being hauled.

Freight Lane

High-volume route corridor used repeatedly by carriers.

Frequent Fueler

Rewards programs at truck stops for fuel purchases.

Full Trailer

Trailer with front and rear axles (not supported by a fifth wheel).

G

GAWR (Gross Axle Weight Rating)

Max allowable weight on a single axle (axle + supported vehicle weight).

GCW (Gross Combination Weight)

Total weight of a loaded combination vehicle.

Georgia Overdrive

Coasting out of gear on a downgrade; unsafe and terminable offense.

G.B.L.

Government Bill of Lading.

Governor

Device limiting maximum vehicle speed (fuel economy/safety).

Grade

Change in elevation expressed as a percentage (e.g., 5% downgrade).

Gradeability

Ability to maintain a given speed on a specific grade.

GVW (Gross Vehicle Weight)

Total weight of a vehicle and its contents.

GVWR (Gross Vehicle Weight Rating)

Max total weight a vehicle is rated to carry (including its own weight).

H

Hazmat

Hazardous materials; requires endorsement and special training.

Headache Rack

Barrier behind the cab to stop forward-shifting loads (common on flatbeds).

Hydroplaning

Tires lose contact with the road due to excess water.

I

Interaxle Differential

Allows tandem axles to turn at different speeds.

J

Jackknife

Tractor and trailer form an acute angle; intentional for parking or accidental.

Jackrabbit Start

Releasing the clutch too quickly so the vehicle lurches forward.

Jake Brake

Engine retarder used to slow the vehicle, especially downhill.

Johnson Bar

Trailer hand valve used to test trailer brakes; also called trolley valve.

K

Kingpin

Pin under the trailer nose that locks into the tractor’s fifth wheel.

Kingpin Lock

Lock placed over the kingpin to prevent unauthorized coupling/theft.

L

Landing Gear

Retractable legs supporting a trailer when unhooked.

Layovers

Off-duty time away from home between loads.

Loaded Call

Driver notifies dispatch from shipper once trailer is loaded and bills signed.

Lift Axle

Extra unpowered axle lowered only when loaded to meet weight limits.

Linehaul

Moving freight from point to point between terminals/cities.

Load Locks

Expandable bars secured across trailer walls to restrain cargo.

Log Book

Record of driver hours of service and duty status.

LCV (Long Combination Vehicle)

Tractor with two or more trailers operating over 80,000 lbs GVW.

Low Boy

Very low flatbed trailer for oversize/heavy equipment.

LTL (Less-Than-Truckload)

Freight under ~10,000 lbs consolidated with other shipments.

Lumpers

Casual laborers who load/unload trailers for a fee.

M

MVR Report

Driver’s motor vehicle record (violations, accidents, etc.).

Mini

Shipment under 100 pounds.

N

No Touch

Driver does not load/unload the cargo.

O

Omnitracs (formerly Qualcomm)

Satellite comms/tracking; can monitor speed, braking, idling, etc.

Opti-Idle

System that auto-starts/shuts engine to maintain cab temperature while reducing idle time.

O, S, & D Department

Overage, Shortage, and Damage department handling cargo discrepancies.

Out of Route

Miles exceeding carrier’s standard city-to-city mileage.

Overage

Extra freight shipped in error.

Owner-Operator

Independent contractor who owns/operates their truck(s)/equipment.

P

P&D (Pickup & Delivery)

Local collection and drop of freight.

Pallets

Wood bases for goods; forklift-friendly.

Pay Load

Weight of the cargo being hauled.

Peddle Run

Route with frequent, multiple deliveries.

Piggyback

Semi-trailer reinforced for rail flatcar transport.

Piggybacking

Loaded highway trailers shipped by rail to a railhead; then moved locally by truck.

Pigtail

Coiled electrical line from tractor to trailer.

Pintle Hook

Coupling used in doubles/triples and truck-trailer combinations.

Placard

Hazmat signage on all four trailer sides indicating material class.

Power Divider

See Interaxle Differential.

Private Carrier

Company hauling its own cargo as part of its business.

PTO (Power Takeoff)

Device transmitting engine power to auxiliary equipment.

Public Scales

Scales available for general public vehicle weighing.

Pull Trailer

Short full trailer with front and rear axles; long tongue.

Pup Trailer

Short semi-trailer (≈26–32 ft) with a single rear axle.

Q

Qualcomm (see Omnitracs)

Legacy name for Omnitracs satellite comms/tracking.

R

Receiver

Customer/consignee accepting the shipment.

Relay Driving

Driver takes a load part way then hands off to another driver.

Reefer

Refrigerated trailer or the refrigeration unit itself.

Retarder

Device assisting service brakes (engine, hydraulic, or electromagnetic).

Rider Policy

Company rules for carrying passengers in the truck.

Runaway Truck Ramp

Emergency escape ramp on steep downgrades for trucks with failed brakes.

Ryan Recorder

Temperature monitoring/recording device in a reefer trailer.

S

Seal

Tamper-evident band on trailer doors; proves doors remained closed.

Semi-trailer

Trailer supported by its own rear axles and by the tractor’s fifth wheel at the front.

Service Plaza

Turnpike/toll-road plaza with parking, restrooms, food, etc.

Shag

Local trailer movement/delivery (yard move).

Sleeper

Sleeping compartment behind/integrated with the cab.

Sliding Tandem

Trailer tandem that can slide to adjust axle weight and KPRA length.

Sliding Fifth Wheel

Adjustable fifth wheel to redistribute axle weights and length.

Slip-seat

Driver rotates among available tractors instead of having a dedicated truck.

Space Cushion

Safe distance around a vehicle to avoid collisions.

Spread Axle

Tandem spaced wider (e.g., 8–9 ft) so each axle is weighed independently.

Spotter

Yard driver moving/parking trailers in a terminal yard.

T

Tandem Axle

Two axles grouped closely together (tractor drives or trailer tandems).

Team Driving

Two drivers alternate driving/rest to expedite transit.

TL (Truckload)

Shipment large enough to fill a trailer (usually >10,000 lbs).

TL Carrier

Carrier dedicating trailers to single-shipper loads (vs. LTL consolidations).

Tractor

Truck designed to pull a semi-trailer via a fifth wheel (highway tractor).

Tri-axle

Three axles grouped together.

Trip Leasing

Booking available “overbooked” loads from other carriers for a single trip.

Truck

Vehicle carrying cargo in a permanent body on the chassis; may also tow a trailer.

Truck-Trailer

Combination of a cargo truck towing an additional trailer.

W

WIM (Weigh-In-Motion)

System that weighs vehicles while moving, typically before weigh stations.

Transportation Definitions

Carriers & Roles

Motor Carrier

Company providing truck transportation (private or for-hire).

Private Carrier

Hauls its own goods as part of its primary business.

For-Hire Carrier

Hauls cargo for others for payment; may be common or contract carrier.

Freight Forwarder

Arranges transportation and assumes responsibility; consolidates LTL to TL and breaks out at destination.

Broker

Arranges transportation via for-hire carriers but doesn’t assume cargo responsibility/possession.

Note: These definitions are simplified. For legal definitions, consult applicable regulations and case law.