Most truck engines don't actually emit large amounts of CO2 as they run on Diesel, the engines typically have very high compression ratios, super/turbo chargers and all sorts of high-tech features that the average SUV engine has never heard of. This results in them emitting higher levels of pollutants like NOX (Nitrogen Oxides) - which are not greenhouse gases, merely responsible for the photochemical smogs and eventually acid rain.

Trucks do however emit lots more visible pollution than cars and lots of particulates (so called PM10s), which are proven to be very carcinogenic.


You can thank all the trucking companies/assosciations/lobbyists for that one...Europe has had clean diesel laws in effect for a few years now, and this in turn has led to clean and powerful diesel engines for cars. (eg VW's 1.9TDi, 130BHP & 50mpg)
In the meanwhile, US is lagging (again), so the US equivalent of that same engine only outputs 90BHP.... so few people actually buy diesel cars.

Fortunately, that will change in the near future. I can't remember exactly when, but IIRC, the clean diesel laws will come into effect in 2004.