You know you're a biking commuter if:
You get in the car for a change, and find yourself slowing to 10 mph to let the cars by before going to the left lane for a turn.
The tires in the car have slow leaks, but you're used to pumping up tires before a trip already, so why fix them?
You look up for that helmet mirror when you're walking down the hall.
You don't know anything about all the uproar over tearing up Parking Lot M next week.
You know how many seconds each phase of the walk-don't walk cycle takes for 8 different intersections.
You roll your eyes when the weather guy says "and you'll have to scrape your windshields off this morning."