What minimum air pressure is typically indicated by dashboard lights?

The minimum air pressure indicated by dashboard lights is generally around 20 psi. This threshold is critical for ensuring that the air brake system in a combination vehicle is functioning properly. If the air pressure drops below this level, it signals that the vehicle's air brake system may not have enough pressure to operate safely and effectively, which can lead to brake failure.

Dashboard lights serve as an essential warning tool to alert the driver to any significant drops in air pressure that could compromise safety. When these lights activate, it serves as a prompt for the driver to take necessary actions, such as safely bringing the vehicle to a stop and addressing the issue. Maintaining proper air pressure is vital in ensuring both the functionality and safety of the braking system, making the 20 psi threshold a critical standard in the operation of combination vehicles.