TROY, Mich. Call it a project worth watching.

ArvinMeritor and Wal-Mart have agreed to develop a dual-mode, diesel-electric drivetrain for over-the-road trucks.

The drivetrain will be developed for use in an International Class 8 ProStar tractor and use an engine developed by Cummins.

"We've been working on development of hybrid drivetrains for some time," said Carsten J. Reinhardt, president of 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 market in a number of important environmental and economic ways."

ArvinMeritor will provide such components as axles, regenerative braking system, air-disc brakes, advanced ABS with integrated stability control and driver assistance systems, software, electronic controls, transfer case, motors, as well as the battery power from a third party.

A key driving force behind the project is Wal-Marts announced intention to double yes, double -- the fuel efficiency of its fleet of heavy-duty trucks during the next decade.

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.