True or False: All vehicles with air brakes must have a low air pressure-warning signal.

The statement is true because all vehicles equipped with air brakes are required to have a low air pressure-warning signal. This safety feature is crucial as it alerts the driver when the air pressure in the braking system drops below a certain level. Low air pressure can lead to brake failure, which poses a significant safety risk to both the driver and other road users.

The requirement for this warning signal is stipulated in regulations governing commercial vehicles and is designed to ensure that drivers are informed of critical system issues while operating their vehicles. Therefore, having a low air pressure-warning signal is a standard safety feature aimed at preventing accidents and promoting safe driving practices.