The next generation of trucks of all categories may well be running with axles that generate electricity on downhill sections or while braking, to store that electrical energy in the onboard battery systems.
The B-double of the future may well have trailer axles generating electricity to power the refrigeration units of a typical fridge pan, plus benefitting hill climbs and when accelerating by adding motive power from hub mounted electrical motors. The end result is less fuel use, greater efficiency, improved vehicle performance and an expectation of reduced total operating costs.