Glossary of Tractor Trailer Wreck Terms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #

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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 hills.