Originally Posted by Elkhound

You come out to start your ride and find that your normal commuter has a flat. If you have only one bike, you call your boss and tell her you'll be late; if you have a second, you commute on that one that day. Your commuter has to go into the shop for an overhaul on Saturday and isn't ready by Monday (or the shop is closed on Mondays). That's when you ride your second. You have to run by the grocery store or the home improvement store after work; you commute on your cargo bike.