I live in Denver, and my home is so far from my office that I quickly got tired of fighting rush hour traffic on the highways. So I started taking the train, which takes longer but is much more relaxing. Then it occurred to me that the bike trails I frequently use go right by my office, so today I commuted by bike for the first time. It took longer than the train, but of course I got a great workout (and I'm about to get another one on my trip home). Plus, if I ever decide during the workday that I'm not up for a ride home, I can just take my bike on the train and get back that way.

This could become habit-forming.