[shinecantbeseen]

That's hard to do in practice, I think. To take the inverse example: in NYC tolls on cars are used to pay for capital projects for the public transportation system. If these "independent" components were truly as independent as you imply income taxes + fares would cover the MTA, but they don't.

Each style of transportation is going to have different levels of cost associated with it, likely changing as one or the other has seemingly stable infrastructure for its needs at the time. It really seems like a more useful perspective is to look at the transportation system as a whole and consider any contribution to car infrastructure, public transport, etc as a contribution which makes the whole system better as a whole.

[nehal3m]

That's not an unreasonable take in my opinion, but then the point of the person I'm responding to is 'let's silo costs and let the market decide' and if we're going to do that, however unpractical, I'd bet a lot of money that driving a car would become unaffordable.

[Ajedi32]

I'd take that bet, were I a betting man. There are 0.85 vehicles per capita in the US. Making roads an average of 1/0.85 = 17.6% more expensive for car owners is very unlikely to break the bank for any significant number of people.