[NachtRitter]

It's probably not something that "can't" be done (or, said more correctly, it's probably something that "can" be done)... But I agree with Frank Lee... there is additional cost, there is additional vulnerability... and the consumer is the one that will pay for that... what is the benefit for the consumer? If the consumer is looking to buy a truck or SUV, then the consumer will have specific reasons for making that choice and it's unlikely that fuel efficiency and lower emissions are going to rank very high on that list. I would not want to pay extra for something that I don't even want.