> If you want to "fund" public transport, you should do it through increased taxation on cars (especially luxury cars) and air travel (in particular private aviation), but ultimately public money doesn't necessarily need to be entirely offset through taxation if it's federally supplied.
I don't think public transport should be entirely free just from both an economic but also ecological POV: despite how much more efficient public transport is on a per-user basis, it's still not free (both environmentally and economically).
There's a recent report by a large public transportation company in Germany which illustrates some of the problems: During the pandemic Germany introduced the "€9-ticket", a ticket that, as the name suggests, costs only €9 and gave you public transportation for ~3 Months (Let's call that free for the sake of argument).
After the end of that program there was a report by (I think) the state Hesse that looked at how public transportation usage and car usage behaved.
The result was that there was massively increased public transportation usage, but not a massive reduction in car usage.
In effect (and from personal, anecdotal experience) free public transport lead to an increase in "fun drives" (e.g. to vacation destinations), but not a decrease in work related transportation.
One of the reasons might be that public transport usage is often fundamentally misunderstood. A significant number of people use a car, not because they want to, but because it is their only option: People living in cities already use public transport, while rural areas (and I count everything with For example, despite living in Germany (which overall has good public transportation) I couldn't travel from the close city (~20min drive) home on any weekday past 10:00PM.
That is despite the fact I still live in a town of ~20k people.
I don't even fault the people that made the decision not to drive busses here: If I drive in that 10:00PM bus, it's consistently half empty (or worse: I've also been in that bus with only 2-3 others, including the driver)!
The solution isn't to tax cars to high heavens, as that decreases the likelihood of people moving outside of cities. Too many people inside cities yields its own share of well-known problems, like high rent prices due to high demand for a, by definition, limited amount of space (density = people/area).
I think the solution for this is much simpler: Specifically subsidize work related transportation by giving people money proportional to the maximal transportation costs (which usually will be a car). This prevents subsidizing "fun drives", while also encouraging people to use public transport when available. This money can be clawed back from employers, which also encourages them to offer e.g. work-from-home (which from both an environmental and congestion POV trumps even public transport).
Since transportation is now well supported via taxes, we can use the saved money to increase public transport where it is logical: people living outside of high density areas _should_ use a car because building a public transport system has too high of an environmental overhead (though stuff like ample parking should exist outside of any high density area to allow for a switch from car->public transport)
Stuff like luxury cars or private air travel obviously should also be taxed, but not because it's transportation, but because highly expensive items for the 1% should be taxed in _any_ case (e.g. an idea would be a progressive VAT which is low for cheap items like food, but high for expensive items like private jets).