ArvinMeritor Inc and Wal-Mart Transportation have agreed to develop a dual-mode, diesel-electric drivetrain for a Class 8 tractor. The vehicle, 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 an engine developed by Cummins Inc.

ArvinMeritor will provide the tandem axle, regenerative braking system, air disc brakes and ABS with integrated stability control and driver assistance systems, software, electronic controls, transfer case, motors, and the battery power from a third party.

In the next 10 years, Wal-Mart plans to double the fuel efficiency of its 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.

The engine also charges an onboard energy storage system, which provides power to the electric motor when demand is high. Energy generated during braking is captured and stored using regenerative braking.