ArvinMeritor and Wal-Mart Transportation have agreed to develop a dual-mode, diesel-electric drivetrain for a Class 8 tractor (heavy truck).

The vehicle, which is believed to be the first dual-mode diesel-electric tractor prototype in development in North America, will be based on an International Class 8 ProStar tractor and powered by a Cummins engine.

"We've been working on development of hybrid drivetrains for some time," said Carsten Reinhardt, president of the ArvinMeritor's commercial vehicle systems business. "This Class 8 project is a major step in our continuing work in alternative drivetrain development - both for power transmission and emissions - and holds tremendous promise for the worldwide heavy-duty trucking market in a number of important environmental and economic ways."

ArvinMeritor will provide the tandem axle, regenerative braking system, air disc brakes and advanced ABS with integrated stability control and driver assistance systems (from Meritor WABCO Vehicle Control Systems), software, electronic controls, transfer case, motors, as well as the battery power from a third party.

Wal-Mart, a global supermarket operator based in Arkansas, had announced earlier that in the next 10 years, it intends to double the fuel efficiency of its US fleet of heavy-duty trucks.

Dual-mode diesel-electric drivetrains, which have both mechanical and electrical propulsion systems, use the electric motor drive primarily for periods of high demand under low-speed, high-load operating conditions, such as accelerating from a stop.  Once moving, the mechanical propulsion system begins to blend its power with the electric motor until it reaches highway speeds, where the drive phases to completely mechanical.  The electrical system can provide additional power during hill climbing, even at highway speeds.

In addition to its work at highway speeds, the engine also charges an onboard energy storage system, which provides power to the electric motor when demand is high.  Energy that is generated during braking is captured and stored using regenerative braking.

In March 2005, ArvinMeritor announced an arrangement with Unicell on a commercial pick-up and delivery program with an ArvinMeritor alternative drivetrain, featuring the company's electric axle and system integration of motors, gears and controls.  It offers zero emissions and fossil fuel consumption, a 10% increase in driver productivity from vehicle enhancements.

The end-user customer is considering a larger order of the vehicle, ArvinMeritor said.