Economics
I've been bicycling to school since Spring of my freshman year. Until this time last year, I lived five miles away from Reed.
(5 miles) (2 trips/day) (5 days/week) (32 weeks/school year) (1 school year) = 1600 miles
Spring of last year, I moved a little further-seven miles away from Reed.
(7 miles) (2 trips/day) (5 days/week) (32 weeks/school year) (1 school year) = 2240 miles
(1600 miles) + (2240 miles) = 3840 miles
Before I sold it in favor of the biking, my trusty Volvo got about 15 miles to the gallon in-city. Let's be real generous, and say gas has averaged $1.50 a gallon.
(3840 miles) ((1/15) gallons/mile) ($1.50/gallon) = $384
Disregarding the cost of my bike (which is valid because it was a one-time cost, and we're also disregarding the whopping one-time cost of purchasing a car), I've spent a little on bicycle maintenance in that time.
(2 new brake pads) ($5/brake pad) + (4 new tubes) ($4/tube) + (2 patch kits) ($1.50/patch kit) = $29
($384) - ($29) = $355
I'll stop just short of spelling out the moral for you.
Now, if you'll excuse me, I think I'll bike to the coffee house and buy myself 300 double mochas.