Home › CDL Practice Tests › General Knowledge Questions › Question 114
Which statement about engine, exhaust, hydraulic, and electric retarders is correct?
- A.They work only when the service brakes have failed
- B.They increase speed on downgrades to save fuel
- C.They slow the vehicle without using the service brakes, but they cannot bring it to a complete stop or hold it parked
- D.They are a full substitute for service brakes
Correct answer
C. They slow the vehicle without using the service brakes, but they cannot bring it to a complete stop or hold it parked
Why
Retarders create braking force at the drive wheels through the drivetrain and are meant to save the service brakes for when they are really needed. You still need foundation brakes to stop fully, and retarders provide no holding force at a standstill.
Manual topic: Basic Control - Retarders · From the General Knowledge practice bank (GK-114).