Compression Brakes are secondary braking systems designed to prevent Air Brakes from overheating and brake fade.

Also known as Engine Brakes or Jacobs "Jake" Brakes these devices work by releasing the pressure from the combustion chambers, thus slowing the engine, thus slowing the truck. Trucks pulling heavy loads of the legal 80,000 pound limit (90,000 in Canada) take a heavy told on the brakes. Prolonged use of the standard air brake system can cause the brakes to overheat and become useless creating a condition known as brake fade. This typically happens when trucks pulling heavy loads must negotiate steep grades down hill. Activating the Jake Brakes slow the truck with out creating wear on the air brakes.

When Jake Brakes are used the sound of the pressure leaving the engine creates a loud overbearing (but cool) noise. This is often the the fluttering sound that can be heard before trucks come to a stop. Some cities and towns have passed ordinances which prevent truckers from using Jake Brakes while in city limits and residential areas. Their use on the highway however is allowed. Coach buses can also be fitted with Jake Brakes but because buses are in city limits more often than trucks they are often fitted with Engine Retarders or Braking Retarders instead.