dalmore - One more thing to consider about that 14%, you're only talking about the emissions from driving the vehicle. To my knowledge there has only been one study done on the subject, but it found that the process of manufacturing one, Focus-sized automobile produced the same volume of emissions as driving the car for 66k miles. When calculating the effect of automobiles, many people forget to add manufacturing and disposal into the equation. Throw in the impact of creating and maintaining the excess infrastructure that the automobile requires and I find it very hard to believe anything has a larger total polluting effect, at least in the US.