I watch the maniacs in the cars jamming on the gas and the brakes, while freaking out, while I get a little exercise. I don't do it to be green. I do it because I'm free. No matter how much horsepower or torque you've got, you're still at the mercy of some dingbat who's going half the speed limit or who's really not fit to be behind the wheel. On the mountain bike, it's a win/win.