[cmccabe]

Natural gas is a non-renewable fossil fuel. Burning it generates carbon dioxide and particulate matter that causes cancer. It may not be as dirty as gasoline or coal, but it's still the same kind of thing fundamentally.

If we're going to retool the entire transportation infrasturcture-- engines, pumping stations, and refineries-- I think we should aim a little higher than a minor improvement. The big problems with gasoline are the public health problem from exhaust fumes and the fact that we will run out of the stuff eventually. Natural gas doesn't solve any of those problems, and it adds transportation and potential safety problems that gasoline doesn't have.

I'd be interested in hearing from a physicist / engineer how much greater the safety problems are with natural gas. There are articles out there like this: http://www.ksl.com/?nid=148&sid=4772381 But it's not exactly fair to compare a badly done natural gas conversion with a factory-installed unit. I have a vague idea that explosive gas is bad, mmkay, but it would be interesting to hear whether it could be made safe.

Interestingly enough, I think the safest vehicle in a crash is probably a diesel vehicle, since unlike gasoline, natural gas, or batteries, a spark cannot ignite diesel fuel under normal atmospheric pressure.