This was 10-15 years ago, so I don't have my notes lying around. However, I do remember that it was based on the calorific efficiency of bread bought at a super

This was 10-15 years ago, so I don't have my notes lying around. However, I do remember that it was based on the calorific efficiency of bread bought at a supermarket. Other foods may vary - for instance if you grow potatoes in your back garden then it's probably going to be a lot more efficient. I can well believe that there is a 10:1 ratio between energy in and mechanical energy out of a human. However my point wasn't that cars and humans are about the same. That's probably only true in the "same order of magnitude" sense. My point was that humans are way less efficient at propelling a bicycle than an electric motor is.