Hydraulic assist for Hybrids make a lot of sense and Peterbilt has certainly got some smart folks their and Kenworth is also on the leading edge with their use of Electronic – Hybrid Technology strategy. Re-designing the modern Truck electrical system also makes sense for saving fuel.
Changing over to a 42-volt electrical system will allow electricity to run many of the components that normally put large loads on the motor and burn more fuel. This is considered a mild-form of hybridization as defined by the Department of Energy:
Mild hybridization typically refers to the incorporation of a 42-volt electrical system on a vehicle. The 42-volt electric system increases electrical power thus allowing the use of electrically powered systems such as electric power steering, electric brakes, and electromechanical value actuation.
You see, by using a more powerful electrical system the truck will have the electrical energy to run more taxing components. When you move the steering in a truck or put a load on the engine for an air-conditioner system or a fan to cool the vehicle that means it takes more horsepower from the engine.
When the engine speeds up to compensate it uses a lot more energy and that means more fuel, so if the goal is to save fuel then it certainly makes a lot of sense to put less of a load on the engine and run it a much lower power setting and this is why the concept of 42-volt electrical systems is being considered and why the engineers designing these systems have had so much success with them.