Bikes are definitely not enviromentally sound machines. Like it has been said, most are tuned to optimize every last cc for power, not economy, or emissions. Just think how easy getting through traffic would be if every SUV you saw with one person in it, was just a motorcycle? The main reason I don't use my bike is helmet head. It would be great if I wouldn't have to worry about how my hair looks for work. Trying to get it from looking like I just woke up is a pain in the butt.