A dual air brake system has two separate air brake systems, each with its own air tanks, hoses, lines, etc. Both systems are controlled by the one brake pedal. Typically, the primary system operates the brakes on the front axle (and possibly one rear axle as well), and the secondary system operates the brakes on the rear axles. Even if one system totally fails, the driver will be able to make a controlled stop using only the foot valve on the other system, although maximum braking power will be reduced.