An application pressure gauge shows the air pressure
- being applied to the brakes. ✓
- that has been used during the trip.
- at which the air compressor will cut in.
- in the tanks.
Answer: A. being applied to the brakes.
An application pressure gauge shows the air pressure being applied to the brakes.
Why this is the answer
The handbook describes optional application pressure gauges as showing the actual pressure delivered to the service brakes. That is the pressure you are applying with the foot valve or trailer hand control, not the total air in the tanks. So when the gauge moves as you brake, it tells you how much air pressure is reaching the brakes at that moment. This matches pressure being applied to the brakes.
Why the other answers are wrong
- B. that has been used during the trip. — A gauge showing pressure used over a whole trip would track accumulated use, but the handbook says this gauge shows pressure delivered to the service brakes when applied.
- C. at which the air compressor will cut in. — The pressure at which the compressor cuts in relates to the compressor governor, while an application pressure gauge shows pressure delivered to the brakes.
- D. in the tanks. — Pressure in the tanks is shown by reservoir pressure gauges, which are separate from an application pressure gauge.
Remember it
Think of the application gauge as a brake-pressure gauge: it follows your foot, not the tank.