I would say that as a bicyclist, I pay general taxes that pay for the roads. I'd also say that as a bicyclist, I don't cause damage to the roads because I'm very light. I'd also point out that as a motorist, I've already paid all the other taxes road-users pay.

So really, as a bicyclist/motorist, I pay the same taxes as other motorists, but cause less of the damage (and create less need for new road construction.)

End of argument.