A hybrid powertrain that uses hydraulic pressure to recover energy normally lost during braking will be tested in a fleet of Ford E550 vans in commercial service, according to the manufacturer. The system, which was jointly developed with Eaton Corp., could cut fuel consumption by up to one-third in stop-and-go driving conditions. The demonstration fleet is expected to go into service in early 2004. The Ford hydraulic power assist (HPA) system uses a reversible hydraulic motor to compress the fluid with energy supplied by a braking vehicle, essentially capturing energy lost as heat in normal brake systems. The stored pressure is then use to help launch the vehicle from a stop, cutting fuel consumption and exhaust emissions. Ford says its research indicates that such a regenerative braking system is best suited to commercial van or medium-duty truck applications where driving cycles could offer a rapid payback through reduced fuel costs. The hydraulic assist system also offers significant performance improvements with computer modeling tests showing a 37% improvement in 0-30 mph acceleration times for an E550 loaded to 19,000 lbs. Ford also expects that the HPA powertrain would cut brake wear by more than 70% in vehicles with GVWs over 8,500 lbs.