What does the air supply pressure gauge indicate?

The air supply pressure gauge is specifically designed to provide critical information about the air pressure available in the air brake system of a vehicle. This gauge indicates the amount of compressed air in the system, which is essential for proper brake function. In a vehicle equipped with air brakes, adequate air pressure ensures that the brakes can engage and disengage effectively, directly impacting safety and performance on the road.

When the air supply pressure gauge shows a healthy level of air pressure, it confirms that the air tanks are adequately charged and ready for use. Insufficient pressure could signal potential issues within the air supply system, such as leaks or compressor problems, which could compromise braking ability and safety.

Other options listed do not relate to the function of the air supply pressure gauge; for instance, the amount of fuel remaining pertains to the vehicle's fuel gauge, speed is monitored by the speedometer, and brake temperature would require separate monitoring tools. Hence, the correct answer focuses on the gauge's role in monitoring the air pressure critical for air brake operation.