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ArvinMeritor and Wal-Mart to Develop Hybrid Drivetrain for Class 8 Tractor

ArvinMeritor, Inc. and Wal-Mart Transportation have agreed to develop a diesel-electric parallel hybrid drivetrain for a Class 8 tractor. The vehicle 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 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 pack from a third party.

We’ve been working on development of hybrid drivetrains for some time. 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.

—Carsten J. Reinhardt, president ArvinMeritor Commercial Vehicle Systems

Wal-Mart has announced that in the next 10 years, it intends to double the fuel efficiency for its fleet of heavy-duty trucks. (Earlier post.)

The hybrid drivetrain will 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, and a ten percent increase in driver productivity from vehicle enhancements. The end-user customer is considering a larger order of the vehicle.

Other Class 8 diesel-electric parallel hybrids under development include projects by Mack Trucks (earlier post) and Eaton (earlier post).



With the dual drive axles of a truck could you implement a cheap parallel system where the mechanical and electrical propulsion were completely separate?

hampden wireless

While I am not against this, it would make more sense to make most postal delivery, ups truck and trash truck hybrids before going after class 8's. Class 8's spend most time on the highway running at a pretty good efficiency point. Eliminating truck idling would also be a better target.

John  Ard

That's not a bad idea, but it would be pretty tight to package that in a standard truck. But it could be a retrofit since the front (middle) axle does the primary driving (the second is only for getting out of a hole or whatever).


"Wal-Mart has announced that in the next 10 years, it intends to double the fuel efficiency for its fleet of heavy-duty trucks."

13 mpg for a semi will be awesome, i hope i live long enough to see it.

i've always heard that boat tails for semis would really help with the mpg's yet one ever uses them. also a flex curtain between the tractor and the trailer, never see those either.


should have typed
"i've always heard that boat tails for semis would really help with the mpg's yet no one ever uses them."

Lou Grinzo

hw: It's not an either-or situation. Wal-Mart can go after these trucks, and other companies can go after local delivery trucks at the same time.


Think of the downhill regerative energy recovery. The big semi has used huge amounts of fuel bringing the full load to the top of the interstate hill and now can recover a lot of that energy on the other side. You bet this will help on the open highway.

joe blow

it is pretty sad that a retail company has to make changes to trucks because none of the truck manufactures have the will and/or intelligence to innovate by themselves


CalStart and WestStart have been working with the truck makers for years on hybrids. Walmart has been on a green spin kick for a while, which is probably why we are seeing this announcement.


a couple of months ago Wal-Mart fired their public relations firm. the new PR company they have, may be responsible for this green spin.
wal-mart is spreading a green message about how they no longer allow any of their trucks to idle for more than 3 minutes and that they have this small diesel unit called a tripac from thermo king... the story i got from one of their drivers was that the tripac units were added to appease a new york judge who was going to fine them big time for having broken NY's idling laws so many times.

Barry R. Guthrie

I'm not clear on exactly what they are trying to do with this implementation of hybrid technologies. It seems like they are taking all the problems characteristics of smaller hybrid cars and exploding them all the way up to class 8 trucks. How much energy are they trying to recover in a fully loaded class 8 truck? How are they storing the energy that would be recovered?

"Energy that is generated during braking is captured and stored using regenerative braking."

It does have a worthy benefit if your truck is operating in a hilly region. With long-haul trucks you will be exposed to all different terrains and regenerative braking may be ok. The problem is, like with cars, the size of the batteries or ultra caps needed to store class 8 braking energy would be enormous and add tremendous weight to the system. The electrical motors would also be significant in size and weight. I'm not sure that when you factor all these system weights for very large electrical capacity in what you can recover and use if you would even be on the positive benefit side of the equation in comparing the fuel you would be capable of saving, plus all the very expensive costs storage system batteries and/or ultra caps and huge motors.

If we can't do it with cars I'm not sure it would be wise to try and do it with class 8 trucks.


One wonders why they have selected an electric hybrid when hydraulic hybrids appear to show great promise for trucks, with more regeneration and storage for less cost and weight.


What battery technology are they using?

tom deplume

I've for a long time wondered why if a diesel-electric drive makes sense for trains but not for trucks.

Barry R. Guthrie

Diesel-electric drives are used in switch yard locomotives (switchers). Here they design the locomotive specifically for adding and removing train cars to build the train structure. There is a tremendous amount of back and forth/stop and go actionss as the train structure is being built. I believe this is probably the best application for hybrid technologies that has real benefit. The added weight of the battery or ultra caps is not too much of a hinderence because this added weight helps with traction to the rails. But the tremendous energy storage and motor system weight is still extremely considerable and needs to be addressed with better technologies.

Ian Williams

A Class 8 Long Haul/ Over-the-Road Truck is one of the last places that a hybrid system will be effective. Every extra pound of hybrid components is one less pound of freight that can be moved.

Hybrid technology is great for the urban duty cycle of UPS package cars or garbage trucks etc.

Long Haul tractors spend almost all of their working life crusing at the speed limit (55-70mpg).

For highway crusing a diesel Jetta does just as well if not better than a Prius of Civic Hybrid.

Boattails and curtains between the tractor and trailer have not yet caught on as they are a large PITA for drivers.

Super single tires that replace duals with a weight and rolling resistance savigns are starting to catch on. I've seen them on Schneider tractors recently.

There is a proven technology that could bost truck fuel ecomony by 30-45%. Its called Long Combination Vehicles (triples, Rocky Mtn Doubles & Turnpike Doubles).


so this system is a parallel system right? they mention the term dual, but almost all hybrids are dual, (electric and diesel power).... does anyone know how deep international is cooperating in this project. they now hav a 4200, 4300 and prostar hybrid prototype, quite deligent.....


SJC - many of the truck manufacturers are already working on this, which is, in part, what surprises me about this announcement. Oshkosh, Eaton, International (schoolbuses with Enova), Volvo (Mack trucks with Enova), UPS, FedEx...

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