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Engine Brakes

An engine brake is a mechanical system used on large vehicles that slows the vehicle by using the engine itself rather than the wheel brakes. When activated, it alters the normal engine cycle to absorb energy and reduce speed, particularly during downhill travel or deceleration.

Engine brakes are commonly known as Jake Brakes or retarders. The term “Jake Brake” comes from Jacobs Vehicle Systems, which developed the most widely used version of the technology.

The system works by converting the engine into an air compressor that resists the motion of the vehicle. This resistance slows the truck without relying on friction brakes. The rapid release of compressed air through the exhaust produces a sharp, staccato roaring noise that can be heard over a wide distance.

Originally developed for heavy-duty diesel semi-trailer trucks, engine braking systems are now also used on tow trucks, buses, utility vehicles, emergency vehicles, and some recreational vehicles.

Without properly designed and installed noise-mitigation systems, engine brake use becomes a serious noise pollution hazard for people living near highways, truck routes, or steep roadways.

Jake Brake Device

The device is installed on the top of the diesel engine. The operator uses a switch on the cab to activate it.

Industry

Major manufacturers of engine braking and retarder systems include Jacobs Vehicle Systems, Pacbrake, and Voith Turbo.

Legislation

Each state has a Department of Transportation (DOT) or equivalent agency responsible for inspecting commercial vehicles for safety and environmental compliance.

Many municipalities restrict or prohibit the use of unmuffled compression-release engine brakes. In some jurisdictions, engine brake use is permitted only in emergency situations.

Jake Brake Prohibited Sign

Many communities post signs banning the use of Jake Brakes. This sign was posted in Syringa, Idaho.

See Also

Health
Health impacts, decibel basics, and major agency findings on sleep disruption, stress, and learning effects.