I spent *hours* when I first started riding, trying to figure out how much "cost avoidance" or savings I was doing by riding instead of driving. It was somewhat easy to find the "per mile" cost of the car based on 12,000 miles per year (e.g. 40 cents per mile). It was a little harder to find the "extra mile" cost of driving an extra mile in a given year (17-25 cents). It was very hard to find the amount of SAVINGS by not driving some miles in a year; it all came down to whether you replace a car every X miles or every Y years, how much more is your car worth with 10K fewer miles on it, the "cost of money" by having to buy a car X weeks earlier, etc.

Then, of course, the cost of riding. How long will a bike last, what is the maintenance costs, clothing, "fuel" (e.g. eating a $1.29 Powerbar in a 32 mile ride).

Long story short (for me). Unless you're avoiding having to have a 1st or 2nd car, or your biking cuts down on 50%+ of the miles per year, it seemed to be a wash dollar-wise. But you can always play with the numbers and justify anything (e.g. to convince the spouse that you should be able to buy a new "free" bike).

-=$>Dave<$=-