Last month Peterbilt Motors Co announced that is taking its new medium-duty trucks directly from the production line onto the road. The new Peterbilt Model 330 and 335 Hybrid Electric vehicles are headed out on demonstration tours. The Class 6 Model 330 Hybrid Electric has the integration of the Eaton Hybrid Drive System and the 260-HP PACCAR PX-6 engine that delivers up to 860 ft-lbs of torque. The Class 7 Peterbilt Hybrid Electric Model 335 uses Eaton's Hybrid Electric Power System with an electric motor that assists the PACCAR PX-6 engine with supplemental torque for improved fuel economy. The system stores energy during stopping through a process called regenerative braking, and then reuses it for acceleration.