When are the engine brake and retarder activated?

• A. Pressure is released from the accelerator
• B. The accelerator is pressed to full throttle
• C. The parking brake is applied
• D. The vehicle is in reverse

Answer: (A)

When you lift off the accelerator, both the engine brake and the retarder can slow the vehicle without using the regular service brakes. The engine brake works by changing how the engine resists movement (compression release or exhaust brake), creating a braking effect as you coast. The retarder adds braking through the driveline, controlled by a switch or lever, and is designed to provide additional deceleration without overheating the wheel brakes.

Pushing the accelerator to full throttle would increase engine power and speed, not slow the vehicle. The parking brake is a separate braking system used for stopping or holding the vehicle when parked, and isn’t activated simply by lifting off the accelerator. Being in reverse doesn’t trigger braking either; it just selects a different direction of travel.