5 reasons green vehicles could take off.

Over the past couple of months, I've driven a hybrid SUV, a truck capable of running on ethanol, a "clean diesel" sedan, and an experimental hydrogen-powered fuel-cell vehicle. Oh, and a few plain old gas-powered cars, too. As an auto writer, of course, I try out different types of vehicles as part of my job. But the expanding variety of technologies available to journalists represents new choices that consumers will eventually enjoy, too.