Much of the infrastructure we need is self-financing. Eg bike lanes, transit etc. increase tax base and keep money in the local economy, while increasing foot traffic and retail sales. There’s no reason curing the 20th century’s car hangover shouldn’t be profitable.

If this were true, they would be easier to get done. Borrowing money to finance is fine, but a lot of these projects have to borrow a vet long way in the future, and the longer the term of the loan, the more interest rates eat into the real return from the project.

Secondarily, many prospective borrowers of these projects are already in debt, and have cash flows which are not growing fast enough to borrow more.

> real return from the project.

why should a gov't project need to have any real returns? Social returns is enough. If the city is nicer to live in, if the businesses thrive because of increaed foot traffic, lower car accident rates, cleaner air etc.

The city has to pay the money back at some point. This either requires higher tax rates, reduced services, or a larger pool of money to tax. The first two are quite unpopular.

No good reason- but like I said, check out the price tag; a mile of subway development in the U.S. can cost billions (with a B!) of dollars. Additional foot traffic along that mile couldn't get you that much back.