Mack displayed on Capitol Hill a prototype hybrid electric powertrain for Class 8 heavy-duty trucks that is said to be the precursor to future commercial vehicles. The power train drives an Air Force R-11 6,000 gallon refueler truck built on a Mack RD 6×4 chassis.
The electric motor assists the diesel in launching the vehicle and regenerates energy during braking. This electrical energy is stored in the vehicle's batteries and is used in place of diesel fuel.
The Air Force refueler was developed under a $1.2-million Department of Defense contract Mack received through Southwest Research Institute. Subsequent funding will build on knowledge gained thus far to develop a full hybrid system that can launch a heavy-duty truck with electric power only. The diesel engine will not be required to idle while the vehicle is stopped. This provides even greater reduction of fuel consumed and noise levels associated with vehicles that stop frequently, such as refuse trucks. Most of this additional development is being performed in Hagerstown at Volvo Powertrain North America, supplier of engines to Mack Trucks.