What does a pressure gauge indicate in an air brake system?

In an air brake system, the pressure gauge is crucial for monitoring the air pressure within the system and indicates the current PSI (pounds per square inch). This measurement is vital for the safe and effective operation of the vehicle's braking system.

Maintaining the correct air pressure is essential because air brakes rely on compressed air to function effectively. If the pressure drops below a certain level, the brakes may not operate properly, which could lead to compromised braking performance and safety risks. The pressure gauge allows the driver to keep an eye on the air pressure, ensuring the system is functioning within the required parameters for safe driving.

The other options do not correctly represent the function of the pressure gauge in an air brake system. The brake temperature is monitored by different sensors, battery status is related to electrical systems, and fluid level pertains to hydraulic brake systems, not air brakes.