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

The statement is true because vehicles equipped with air brakes are required by federal regulations to have a low air pressure warning signal. This safety feature alerts the driver when the air pressure in the brake system drops to a certain level, which can indicate a potential failure in the braking system. The purpose of this warning signal is to ensure that drivers are made aware of low air pressure before it becomes critical, allowing them to take appropriate action to maintain safe operations. This requirement applies to all vehicles with air brakes, regardless of size or age, emphasizing the importance of having an effective braking system for safety on the road.