Earlier quoted context omitted.
Even if it does, the amount of money allocated from the general fund toward transportation maintenance is surely lower than it would be if those fuel taxes were not there. Unless an earmark pays 100% of the costs of something, the earmark is totally an illusion. Even if it does pay 100% of the costs, it is often mostly an illusion. In practice, most earmarks fall into the former category, and thus are entirely about…
It’s worth pointing out that fuel taxes were sufficient to keep the US highway trust fund self-sufficient for over 50 years. Recently, there’s been a shortfall that has required infusions of cash from the general fund.
Think about it.
Scenario a) X dollars from fuel tax are revenue for federal budget. Federal budget decides whatever it wants to do with the money, but roads require Y dollars for maintenance.
Scenario b) X dollars are earmarked for road maintenance. Federal budget can't do anything else with the money but spent them on road maintenance. Roads require Y dollars for maintenance. X is covered from earmarked revenue, and the difference comes from federal budget.
Did ANYTHING change between scenarios? In both cases taxpayers paid X dollars of fuel tax and Y dollars for road maintenance.
Earmarking tax revenue for a cause that requires greater amount of money and would be covered anyway is just PR mechanism to placate people / opposing party. Opposing party might know it is just illusion but still needs to placate their own constituents.
The goal of this is to create another tax revenue stream without angering your voters. And so we complicate what is relatively simple so that general population thinks the tax is for their benefit. It still is but for a different reasons.