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 manipulating the public. Not that I'm necessarily objecting to manipulating the public.

===

worked example:

If fuel taxes bring in $100, which is spent on road maintenance, and then topped up by $40 of money from general revenue, that implies that the government thinks that $140 is the point at which marginal benefit drops below marginal cost. In other words, if there was no fuel tax, they'd probably still try to spend $140, or thereabouts. The earmark is entirely illusory.

If fuel taxes bring in $100, which is spent on road maintenance, and is not topped up, then that implies that the government thinks that the point at which marginal benefit drops below marginal cost is some number below $100. If there was no fuel tax, their spending on road maintenance would go down. Go down to what? Let us suppose that it would go down to $60. Then the fuel tax earmark is 40% reality, 60% illusion.

Yes, earmarking is smoke and mirrors.

The reality is, roads would be maintained the same way with or without earmarked tax revenue.

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.

Exactly. It doesn't matter where a dollar comes from when it has to be spent anyway.

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.

Per the article, in Australia the fuel excise does not go toward road maintenance, but instead goes into the general fund.

This is true, but the highway trust fund is not funded exclusively by fuel taxes, it's funded from the general fund

https://www.taxpolicycenter.org/briefing-book/what-highway-t...

It’s worth noting that for over 50 years, the trust fund was fully self-sufficient with no general fund contributions. There’s been a shortfall in recent years because Congress is reluctant to increase the gas tax. As fleet fuel economy continues to increase, the tax revenue per mile driven continues to fall.

And in the US, the overwhelming majority of road damage is done by long haul freight semi trucks, not electric or ICE cars.

I don’t see what difference it makes if certain taxes are earmarked for certain expenses. Any shortfall is made up by increasing taxes and/or increasing taxpayer debt, any surplus will result in less assistance from other taxes or get directed elsewhere.

Budgeting is often quite fungible and you can replace where to spend new money by replacing old money.

I would say that 60% of taxes might be raised for health and education this way.

and the article is specifically talking about australia, which doesn't have specific tax buckets for a purpose.

Gas taxes pay less than half of the costs of maintaining roads.