Back in 2011, Mr. Money Mustache wrote an article called The True Cost of Commuting and he meant the cost of car commuting. In the article, he uses the federal allowance for driving which was 51 cents at the time. Currently, it's 70 per mile. Some people think that the cost of driving is not linear per mile, but Mr. Money Mustache argues that it is. Fixed costs are believed to be purchase and insurance, but the less you drive, the less often you need to replace your car. The same goes for repairs. Calculating the only the fuel cost for your distance is wrong. So when you ride 10 miles instead of driving 10 miles, you're saving $7 off your car expenses. I don't know what bike expenses per mile are, but maybe acidfast7_2 does, since he did a study of it (with a sample size of one) a few years ago.