Aren't the majority of CO2 emissions from heavy trucks. I seem to remember a statistic from about 1990 that 90% of the pollution was caused by 10% of the vehicles. At that time, the high-polluting vehicles (mostly trucks, but also old cars) caused 89 times the pollution of the other ones. Granted, this is an old statistic, but large trucks have very powerful backers and have been exempt from most pollution legislation since then.

I would be interested to know what the current statistics are. I imagine that SUVs are worse than small cars but still dwarfed by tractor-trailors in the amount of pollution produced.

-Biscuits