There are a lot of people who could get even more value from a great transit system. However anything less than great a car provides a lot more value and so it is really hard to get there. About 1/3 of all trips done in a car would be worse by any other means (plumbers bringing tools and all spare parts to where there is a problem), but the rest could be done via transit if we had it.

What are the additional costs of cars and their infrastructure when there are more efficient options for transportation?

Irrelevant, we don't have those other systems. Invest in them first. Places like NYC have a start, but they don't make good investments in more. Other cities are trying, but have a lot of work to go.

The bigcorp I used to work for provided every employee with a bottomless metro card that could get you a free bus or train ride anywhere in a 20 mile radius. I would guess that maybe 1 in 5 people ever used it. Give someone enough disposable income that they have a choice between a 20 minute ride with their favorite podcast on the stereo vs. a 40 minute ride lurching along with a bunch of strangers and people tend to pick the first one. Our VP, to her credit, did take the bus every day, though.

Transit doesn't have to be that much worse than the car 'it often is, but it need not

What happens when there is a bunch of investment and they still mess it up?

https://www.tvo.org/article/ottawas-colossal-lrt-debacle-a-b...

Many working people I know who used to take transit before bought cars after the LRT came in.

Lots of places are like NYC and not making good investments. Which is why cars are likely to dominate for the foreseeable future.

My point is the ROI of investments in those systems is much higher than trying to improve car infrastructure. And, necessarily, crashes and costs of cars are reduced along the way.

Maybe. If you waste money like NYC does the ROI isn't there. Even if you don't waste money, a small investment won't have enough of a network effect to have a good ROI.

What does that efficiency metric optimize for? For most americans, switching to public transit means turning their 1-2 hr daily commute into a 3-6 hr. Most americans cannot afford to live in downtowns or near their jobs.