Here's an article from Maxwell Tech. They build a lot of things, but I've kind of followed their Ultracaps for years, (they gave me a little one years ago to play with - I want a bunch of big ones!)

The theory is using a regenerative braking system to charge the caps, (which charge fast), instead of charging the batteries, (which charge slow), and using the caps to power acceleration.

This article talks about using them in gas/electric hybred buses (Triton V-10 engines for FTE content..)

http://www.maxwell.com/news/release.asp?PRID=139

If you're used to seeing capacitors in the uF range, take a look at the specs on these - some are 2500 F (yes, that's Farads).

A bus can't be much different than a one-ton duelly.