But every person who is buying a new car in a given year (usually via a loan they pay off over 3-5 years) is not going to just give that money to the government to build a train line that might be finished in 10 years instead (and they have no transportation in the meantime). That makes no sense. These things are not interchangeable.
This is a well-trodden path. The government finances the projects over a number of years through the capital markets and then levees a tax to cover the payments. They are quite interchangeable. 30% of New Yorkers and 35% of DC residents don't even have access to cars and yet manage to live and get around - thrive even.
It's not replacing the money that gets spent on cars. People buying a new car are buying it because they need it now, they need to get around today, not in 10 years when the new train gets built. They're still going to buy the car and then have to pay the tax to build the transit on top of that.
So you've identified the chicken and the egg, I agree, which is why we finance these things. By the time its built that money won't need to be spent on cars anymore on an ongoing basis.
I'm all for public transport, but lying to people and saying it's going to be zero cost because it will completely supplant what they spend on cars is not the way to get support for it. A train or bus line that goes to 20 specific places and nowhere else is not a substitute for a car that can go directly to any place, whether across town or across the country.
We should absolutely invest in public transport, but let's not pretend it isn't going to take making spending money on it a priority. It doesn't come for free and it doesn't completely eliminate the need for cars.
It also requires the entire development to shift to be much, much denser. It's not like "oh we just issue some bonds to build a rail line and then nobody ever has to buy a car again".
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