Apropos Ravenhog's commute, I spent 6 months in Switzerland last year on a work assignment. The bike commute (or walk, when necessary), was about 1 mile. The kicker was, most of it was on a 10% grade, downhill on the way to work, fortunately. Getting to work by bike was a 5 min job, if that, getting home more like 15 min. In spite of the short round trip distance, there seemed to be a workout in there somewhere.