FedEx Ground, Purolator and UPS will soon deliver packages using hybrid hydraulic parcel delivery trucks.

The companies, members of the Hybrid, Electric and Advanced Truck Users Forum’s parcel delivery working group, announced the receipt of the evaluation vehicles from Freightliner Custom Chassis Corporation, Morgan Olson and Parker Hannifin. FedEx Ground, Purolator and UPS each purchased an evaluation vehicle with assistance from Calstart, through a grant from the US Department of Energy.

These are the first-of-their-kind commercially available hybrid hydraulic parcel delivery vehicles, according to HTUF. The vehicle chassis includes a Parker hydraulic hybrid drive system, designed specifically for medium-duty, start-stop applications such as parcel delivery. FCCC integrated and assembled the drive system, and bodies were installed by Morgan Olson.

Braking energy is recovered and stored in hydraulic accumulators, where it is used to power the truck during acceleration. Parker’s onboard controller incorporates an advanced engine-off strategy to minimize unnecessary run time. As a result, fuel use can be reduced by 40 percent or better based on route profile, the company said.

The three package delivery companies will be cooperating with Calstart and FCCC to gather data on the operation of the vehicles to establish expected fuel economy improvements and reduced brake and engine maintenance costs. Although hydraulic hybrid systems have shown promise over the last few years, commercial deployment of these systems has been limited to Class 8 refuse trucks. This evaluation will assess an efficient hydraulic hybrid system for lighter, Class 6 vehicle applications. Successful demonstration could pave the way for additional purchases of hydraulic hybrid vehicles throughout the trucking industry.

Corporate fleets in the U.S. buy some 300,000 vehicles a year, making them likely customers of hybrid delivery vehicles.

Earlier this month, FedEx Express announced it’s launching a carbon-neutral shipping program.