I ran accross the GE Evolution Hybrid Locomotive and wondered could the same be done for big rigs on the highway?

Yep, and this is what I found. Peterbuilt is already going down that route with the Model 386 Hybrid Electric (HE). Back in early 2007 Peterbilt predicted $9,000 in annual fuel savings (based on an average cost of $2.50 per gallon). It’s probably a bit more savings now that diesel is $4.75 a gallon. Wal-Mart bought the first one to roll off the assembly line in May of 2007.

Peterbilt has even developed a hybrid dump truck this month.

Now I wonder how much it would cost to convert the older trucks?