Which of the following is an auxiliary braking system?

• A. Exhaust brakes
• B. Primary service brakes
• C. Handbrake only
• D. Hydraulic wheel locks

Answer: (A)

Auxiliary braking systems are secondary methods that help slow the vehicle in addition to the primary service brakes. Exhaust brakes fit this role by creating backpressure in the exhaust system to resist engine motion, which slows the vehicle without using hydraulic brake pressure. This engine‑based braking reduces wear on the wheel brakes and is especially useful on long descents or when you want smoother deceleration.

The primary service brakes are the main hydraulic braking system that applies friction at the wheels. The handbrake (parking brake) is intended mainly to hold the vehicle when parked, not for regular deceleration. Hydraulic wheel locks describe a condition or device that would lock wheels via hydraulic pressure, which is not used as an auxiliary braking method.