TRUCK INDUSTRY TERMS & TRUCKING GLOSSARY

[A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [O] [P] [R] [S] [T] [U] [V] [W] [Y]

- R -

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.

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

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
Semitrailer 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.

- S -

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

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 semitrailer, 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.

SUV
Sport/utility vehicle.

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.

- T -

Tag Axle
See Axle.

Tare Weight
See Chassis Weight.

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

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

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
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 semitrailers on railroad flat cars. (see Piggyback)

Tractor
Truck designed primarily to pull a semitrailer 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 semitrailer combination.

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 semitrailers.

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.

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.

- U -

ULEV
Ultra-low emissions vehicle.

Upper Coupler
Load bearing surface on the underside of the front of a semitrailer. 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.

- V -

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.

- W -

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.

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

- Y -

Yard Jockey
Person who operates a yard tractor.

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

[A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [O] [P] [R] [S] [T] [U] [V] [W] [Y]