BPW running gears with air suspension or hydro-pneumatic suspension can be provided with a lifting axle. Lifting axles protect the tyres and reduce fuel consumption.
An additional advantage is that the lifting axle can be used as traction assist. The temporary lifting of the first axle increases the bearing load on the tractor thus improving the traction of the vehicle on difficult terrain.
It has to be considered that the load is then distributed on the axle(s) standing on the ground. An overload of axles as a result of lifting one or several axles is basically avoided.