This fact is always worth repeating:
The amount we spend on roads every year far outstrips the money raised by user fees: “Nationwide in 2010, state and local governments raised $37 billion in motor fuel taxes and $12 billion in tolls and non-fuel taxes, but spent $155 billion on highways,” and the federal government spends about $40 billion more on roads than it takes in from the gas tax.
There’s a zombie idea out there that transit requires subsidies, while the auto infrastructure is fully funded by user fees. In reality, all of the transportation infrastructure is subsidized. One important reason that all transportation modes have to be subsidized is that we don’t capture back the windfall we create for nearby private landowners when we build and operate useful public infrastructure like train stations near their properties.