I think it's hard to generalize that living in Manhattan without a car is safer and healthier than living in, say, Vermont with one--especially if you rent cars for weekend and other vacations. Depends of course on location, lifestyle, commute, etc.

Yes you’re right, and a big factor I didn’t think of is pollution.

The car accident death rate may be low enough that it’s really not worth mitigating against.

But also, I don’t mean Manhattan specifically. When I say “city” maybe you are thinking high rises. A neighborhood with predominately 2-4 story buildings can be incredibly walkable. You just have to stop designing everything to accommodate cars ahead of all else.

Just have to.

So long as that is the requirement it won't be done, nobody will do it. You need to find a different starting place.

Start by not requiring buildings be far apart and have parking. Right not the neighborhood you envision isn't legal to build if you want to. Make it legal.

Make tax codes encourage building high. Charge higher taxes for the ground floor.

Allow everyone to build by right (meaning no public hearings, permits must be approved by buerocrats) up to the road/sidewalk or property line.

Even if the building is setback from the property line require the outside walls be built to up the lot line on all sides standards. That means fireproof if the building next door burns. That means can be demolished without anything falling to the outside, or even a need to do anything outside to demolish it.

For bonus points define places where a door to the next building must be located. (you might never visit your neighbors that way but the door still exists and can be repurposed to a public walkway when you leave and the new owner has other ideas.

Manhattan is certainly an extreme case. Though I'd argue that, in the US, there are a small number of cities where you can live carless without any real compromises. Of course, my definition of compromise may be different from yours; if I lived in the Bay Area I'd be regularly going to mountains/ocean/etc. on weekends. Even a couple I know who live in SF without a car are regularly doing short-term and long-term car rentals in addition to walking, Muni, and Uber. I'm not sure they really are in a car less than they would be if they owned one.

Especially with pollution, however there are also social implications that can change your mortality rates. for example a low stress job in NYC could have great social payoff as you are surrounded in a world with anything and everything. Want to play ping pong with random people? Do it! Vermont is extremely isolating unless you are in Burlington or such.

Unfortunately, we will also have to start taking into account pathogen transmission risk on public transport.

If you have a larger family and a limited budget, suburbs are the best of both worlds.

Also cars are quite reasonable unless you want new ones before their useful life is exhausted. A modern car will usually last 25+ years, which is more than many homes before they need major renovation (new roof, windows, etc. in the US).

Although it's too early to see how everything plays out, there's a fair bit of anecdotal data suggesting that people who can, especially renters, are leaving urban areas for more suburban or rural locations. I know a number personally and there have been various stories about many broken leases in places like the Bay Area.

Easy to say. I live a long walk from work (normally I ride the bus), now they are talking about moving to a different building that isn't served by transit (20 minute walk to the nearest bus stop), since it isn't that far by car they aren't even thinking about offering relocation expenses so it would cost me more than a new car to move (after realtor fees and other moving expenses). There is no reason to believe that this is the last time they move us.