Glossary of Truck Related Terms

Axle
Structural component to which wheels, brakes, and suspension is attached. Drive axles are those with powered wheels. Front axle is usually called the steer axle. Pusher axles are not powered and go ahead of drive axles. Rear axles may be drive, tag, or pusher types. Tag axles are not powered and go behind drive axles. Axes may lock causing truck accidents.

Blind Spot
Areas around a commercial vehicle not visible to the driver either through the windshield, side windows, or mirrors; a common cause of truck accidents

Cargo Weight
The combined weight of all loads, gear, and supplies on a commercial truck or rig.

Common Carrier
A freight transportation company that regularly serves the general public with route service over designated highways. Or irregular routes between various points on an unscheduled basis.

Dead-Heading
Operating a truck without cargo; when an oil tanker is not full, the sloshing creates a dangerous situation conducive to truck accidents.

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

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)

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.

GVW (Gross Vehicle Weight)
Total weight of a vehicle and everything aboard, including its load; could be an important piece of evidence in a truck accident.

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.

Jackknife
To place the trailer at a very sharp angle to the tractor; one of the major causes of truck accidents

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.

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

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

Payload
Weight of the cargo being hauled

PSI (Pounds per Square Inch)
In trucking, unit of measurement for tire air pressure, air brake system pressure, and turbocharger boost. The correct PSI is crucial to braking; inability to brake is a major cause of truck accidents.

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, brings it to a safe stop. Depending on the surrounding terrain, the ramp may be level or run up or down hill.

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.

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 Trailer
Tractor and semi trailer combination

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 and truck accident attorneys

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