I'm going be a contrarian here and say I never thought fuel taxes, tolls or any "user" fees were a good idea to fund roads.
I think it's disingenuous to say "let the user pay." Everyone uses roads, whether we drive on them or just buy the things that other people transported over them.
Transportation infrastructure is one of the few things that I think should be funded by government, out of general funds. The better the roads (and railroads, and airports, and seaports) are, the better our economy - our whole society - works. We ALL benefit.
We have enough ways to collect taxes now. We can argue about which ones are the most "fair," but presumably that's the goal. Just set them at a level which can support our infrastructure and get out of the way.
I agree. But, what I think is missing in this discussion are road investments some people get and others pay for. For example, the road in front of my house has no place to park a car. Some people in town get parking, others don't. We all pay the same price per gallon.
The same is true of cal-de-sacs. Some of us drive around the neighborhood to get to the same place. Others go directly from home. Related to this are motorists who require infrastructure to behave including traffic lights, bump outs, etc. All put in place for controlling motorists that well-behaved motorists pay for. We shouldn't forget the cost of accidents. Police, state response vehicles, etc.
Concrete/tar results in environmental run off. When was the last time you visited a store and could not find parking. Not only is it driving up rental prices causing higher consumer prices but it drives up environmental remediation costs. That is also true about the extra 8- 11 feet of parking in front of many homes, mentioned above.
Then we end up building more and/or wider roads for commuters who in some cases must live far away from work given housing costs. But in other cases do it by choice. While they pay a little more per mile in gas tax as this thread has been discussing, it is likely not their fair share. Adding a freeway lane is VERY expensive. maintaining an old state road, next to a freeway, is also not cost effective to maintain.
Finally there are urban dwellers, who can do many of their errands and/or going to work in non-motorized transport but don't. The bargain price of roads as a % of income, does not result in non-motorized consideration to reach a nearby destination. Our cost for roads typically encourages a request for more parking, more traffic lights, more roads vs bike lanes or more sidewalks. The excuse is safety, among a few others. Easily remedied if enough people got on board. Check out the Netherlands.
I am not sure this is the best study and it is from Canada but it provides an interesting analysis. While it may not answer every question, it will allow for an interesting presentation of this subject.
https://www.diva-portal.org/smash/get/diva2:935942/FULLTEXT01.pdf