A dual air brake system has two separate air brake systems, each with its own air tanks, hoses, lines, etc. Typically, one system operates the brakes on the rear axle(s), and the other system operates the brakes on the front axle. If one of the systems loses air pressure (causing the low air pressure warning), either the front or the rear brakes won't work properly. As a result, your vehicle's braking distance will increase. If this happens, stop your vehicle and get the system fixed.