WonderMonkey, Just for clarification- when I wrote, "if that is the case for [you] then you're either screwing up the math..." The "you" in this case was not directed at you as the OP but to the general reader and, particularly, those readers that are somehow under the assumption that riding a bike to work has to be a rather expensive proposition.

The variables involved in computing the actual costs of transporting oneself to work/school can be extrapolated into all kinds of complexities (including the costs of Clif bars for a cyclist's ride or the Starbuck's or egg Macmuffin the driver grabs for the drive in every morning) and can be extremely individualized based on the specific commute and commuter. But at it's most basic, general level it is probably 5 x's more expensive, on average, to commute by private auto than it is by bike- even when the commuter owns a car that sits unused in the driveway while they commute to work on their bike.

The posts that astound me are the ones that claim to drive a perfectly running car, which was given to them and for which they pay minimal insurance costs, never breaks down and their commute has no tolls, no parking fees and for some inexplicable reason their employer subsidizes their drive. They then go on to assert that it costs far less to drive than riding their $3500 carbon fiber bike, on their $120 tires that wear out every 500 miles, wearing their full cycling kit, which must be laundered daily or they have several sets, and they must be "fueled" by special nutrients harvested in remote mountain lakes in South America... and that this set of factors somehow applies to everyone, world wide who rides a bike for transportation.