The three main brake systems in modern air brake setups are service brakes, parking brakes, and the ______ brakes.

The three main brake systems in modern air brake setups are service brakes, parking brakes, and the ______ brakes.

• A. Service brakes
• B. Parking brakes
• C. Emergency brakes
• D. Trailer brakes

Answer: (C)

Air brake systems are built around three main braking modes: service brakes, parking brakes, and emergency brakes. The emergency brakes provide a fail-safe that engages if the air supply drops too low or a leak develops, so the vehicle can still be stopped even when the regular brakes can’t be applied. In heavy trucks these are typically spring brakes that stay released by air pressure and automatically apply when pressure is lost. That backup function is why it’s the missing piece in the trio. Trailer brakes exist as part of the overall system but aren’t considered one of the three primary brake modes.

Air brake systems are built around three main braking modes: service brakes, parking brakes, and emergency brakes. The emergency brakes provide a fail-safe that engages if the air supply drops too low or a leak develops, so the vehicle can still be stopped even when the regular brakes can’t be applied. In heavy trucks these are typically spring brakes that stay released by air pressure and automatically apply when pressure is lost. That backup function is why it’s the missing piece in the trio. Trailer brakes exist as part of the overall system but aren’t considered one of the three primary brake modes.