An automatic air suspension control system is provided for use in combination with a vehicle having a liftable non-driven rear axle, a driven rear axle, a parking brake, and an air suspension associated with the rear axles to apply a load to the rear axles. The air suspension control system is programmed to determine whether the rear axles are subject to a load condition under which the non-driven rear axle is to be moved between lifted and deployed conditions. If the rear axles are subject to a load condition under which the non-driven rear axle is to be moved, the air suspension control system also determines whether the parking brake is engaged. If the parking brake is disengaged, then the air suspension control system causes the non-driven rear axle to be moved; otherwise, if the parking brake is engaged, then the non-driven rear axle is prevented from moving.