I (or my accountant) claimed my truck for business use, but that's the only "credit" I know of. I think the law changes about every year on this, but when I first deducted mine a couple years ago, I think the vehicle had to be over 6000# and used at least 50% for business. In addition, there was an accelerated deduction (I think it was/is section 179) that could allow you to deduct it all in one or two years.
My understanding was that the deduction was originally passed into law a couple decades ago, to allow / encourage farmers and small tradespeople who used a heavier truck in their business to get a new truck. Then when the monster SUVs passed 6000#, all the yuppie lawyers and the likes who drive those things and had their own firms began using the deduction -- legally, but outside the spirit of the law. The joke (not so funny) was that they would count their miles to Starbucks for lattes as "business use".