Permo-Drive, a Australian company, has developed the Regenerative Drive System (RDS). When a vehicle is braking, the energy drives oil into a hydraulic accumulator, which is then pressurized with nitrogen. As the vehicle accelerates the oil is pushed through a pump motor to assist the drivetrain. Engine output is reduced accordingly to save up to 35 percent in fuel. Additional benefits include reduced emissions, improved brake life and better acceleration. A story in an engineering magazine says hybrid hydraulic systems weigh less than electric hybrid systems and are less expensive. It also leaves less of an "environmental footprint." The military is testing the system on its large transport vehicles.
[Source: Eureka Magazine]