All air-braked vehicles must have which device?

All air-braked vehicles must have which device?

• A. A supply pressure gauge
• B. An oil pressure gauge
• C. A fuel gauge
• D. A temperature gauge

Answer: (A)

Air brakes rely on compressed air to apply and release the brakes, so you must be able to monitor the system’s pressure. The supply pressure gauge gives a direct readout of the air stored in the system and shows whether there’s enough pressure to stop safely or if a leak or compressor problem is developing. That makes it the essential device for all air-braked vehicles. An oil pressure gauge, fuel gauge, or temperature gauge serves other engine-related purposes and does not indicate brake readiness, so they aren’t required for the operation of air brakes.

Air brakes rely on compressed air to apply and release the brakes, so you must be able to monitor the system’s pressure. The supply pressure gauge gives a direct readout of the air stored in the system and shows whether there’s enough pressure to stop safely or if a leak or compressor problem is developing. That makes it the essential device for all air-braked vehicles. An oil pressure gauge, fuel gauge, or temperature gauge serves other engine-related purposes and does not indicate brake readiness, so they aren’t required for the operation of air brakes.