It was fun reading the six pages of posts here. Transportation economics...which is what this is all about...is a tough nut to crack, for so many of the reasons folks have pointed out.
There is room for some improvement and analysis though. Roads have two cost components: their capital costs (building) and their maintenance (wear and tear). Most people focus only on the latter. The former is usually paid at the state level out of a combination of gasoline taxes and general revenues; and is best levied as a flat fee at registration for any vehicle that uses the roadway, regardless of size. The roads have to be built to accommodate all vehicles from trucks to bicycles, they have to be marked, have lights, signs, traffic monitors (aka cops) etc.
The latter, maintenance from wear and tear is really where we need a much more intelligent system. We have begun to incorporate vehicle wight and axle into excise taxes; a far broader view would be some quantitative measure of "roadway presence" incorporating wight, height, girth, axles, and shape. This sounds complex but the calculations would be very similar to the way FedEx and UPS assign costs for their oddly shaped packages that they carry. Their would be an incremental fee based on some formula incorporating the previous factors. Bicycles would do very well here, as our "roadway presence" is quite light indeed.
The gas tax should be repealed. There is almost no relationship between fuel consumption per mile and roadway impact these days.
My final note is to point out how complex and hair splitting and tear-your-hair-out public choice theory is. This is EXACTLY the reason why we have the concept of limited government, because the private sector makes these decisions every day without blinking while politicians/voters get into a tizzy over it.