Link: http://www.exploratorium.edu/cycling/humanpower1.html
Quote: "The bicycle is a tremendously efficient means of transportation. In fact cycling is more efficient than any other method of travel--including walking!"
The hidden agenda is that such an efficient mode of transport is difficult to tax based on conventional measures like fuel used or CO2 emitted -- although it's apparent that people will try.
I think bicyclists should be taxed based on what their existence costs society as a whole -- freeway construction, pothole repair, global warming, health care for those dying of heart disease and diabetes. By that reasoning, bicyclists should receive a tax credit, like those who install solar panels or buy electric cars.
Oh -- did I mention that I'm a bicyclist?