All vehicles equipped with air brakes must have
- at least one brake heater.
- a tank pressure gauge. ✓
- an application pressure gauge.
- a hydraulic system as a backup.
Answer: B. a tank pressure gauge.
All vehicles with air brakes must have a tank pressure gauge.
Why this is the answer
The handbook says every air-brake-equipped vehicle has at least one air pressure gauge on the instrument panel. That gauge shows the pressure in the service reservoir system, so the driver can check that there is enough air to apply the brakes. It may be a single-needle gauge or a two-needle gauge for the primary and secondary reservoirs. The application pressure gauge is described as something many vehicles have, not as required equipment on every air-brake vehicle.
Why the other answers are wrong
- A. at least one brake heater. — The passages do not say a brake heater is required; they discuss gauges and warning devices instead.
- C. an application pressure gauge. — The handbook says many vehicles have a gauge showing applied air pressure, so it is not equipment that every air-brake vehicle must have.
- D. a hydraulic system as a backup. — The passages describe air brake components and never say a hydraulic backup system is required.
Remember it
Remember: every air-brake dashboard has a reservoir pressure gauge; the applied-pressure gauge is extra.