Sadly there is yet another reason to ride a bike instead of driving a car. Regardless of how 'green' you make operating a motor vehicle, it is still an incredibly inefficient use of energy. The sad irony is that Americans reap the benefits and the poorest people bear the brunt of the suffering. Would it kill you to ride a bike to work one day a week? How about two? If you do it enough you'll stop even wanting to drive, I promise.