Hydraulic-diesel vehicles will be `world`s cleanest`

A group of US organisations is developing a hybrid hydraulic-diesel drive system which, they say, will result in the world`s cleanest, most fuel-efficient, and most cost-effective urban delivery vehicles. They predict that the vehicles will achieve a 90% reduction in nitrous oxide (NOx) emissions, and a 60-70% increase in fuel efficiency, resulting in a $2,500 reduction in annual fuel bills for a vehicle that covers 40,000km a year.

The group, led by the US Environmental Protection Agency, includes Eaton, the parcels delivery giant UPS, International Truck & Engine, and the US Army National Automotive Center. In the first phase of the project they will develop a hydraulic hybrid powertrain with a propulsion system integrated into the drive axle. Hydraulic tanks will store energy when the vehicle brakes, and will release the energy to hydraulic motors when the vehicle needs to accelerate.

The drive system will be fitted to a UPS truck which is expected to recoup the extra cost in less than three years through fuel savings and reduced brake wear.

A second phase will add a "clean diesel combustion" engine which cuts NOx emissions without needing any after-treatment. The drive system is aimed at vehicles such as refuse trucks, buses and parcel delivery vans, which often have to operate inefficiently in stop-go traffic.