So I'm here bringing up an idea which has been brought up before. Why not tax bicycles, their accessories, or their associated services (like repair) to pay for better bike infrastructure: more bike lanes, bike boulevards, sharrows, bike racks, or even public education campaigns?
I think it's a promising idea for several reasons.
1) It would address the biggest obstacle to cycling. In my opinion, the main obstacle to more cycling seems to be bad cycling conditions, not the money cost of cycling. Cycling is ridiculously cheap compared to owning a car or even riding a bus. A small surtax on cycling gear and services probably isn't going to deter too many people, but better riding conditions could have a big impact on inducing more cycling.
2) Gas taxes are less and less able to meet anyone's transportation needs. As cars get more efficient they pay less tax per kilometer driven. Political barriers make it very difficult to raise the taxes. Deferred maintenance on today's infrastructure will add up to higher costs tomorrow. Why be dependent on a funding stream that is increasingly dysfunctional?
3) It worked for cars. Taxing a mode of transportation to improve its infrastructure is a key reason why we have car dominance today. In the 1950s and 60s the interstate highway system was built with gas tax revenue. Although we sometimes think of raising gas taxes as a way to discourage driving, historically they have helped to encourage it by paying for roads.
4) It would be good politics. Providing a direct and visible source of transportation funding from bicycles to bicycle infrastructure takes one more argument away from people who want to portray cyclists as leeching off of tax money they aren't paying into. Also, a tax that only falls on bicycles is less likely to run into conservative blowback than a tax that falls on a broader base of people.