You can solve almost all of those problems more easily by improving road design with knowledge we already have. In relative terms cars are actually amazingly safe given that we drive them trillions of miles a year.

> They're all things that trains and subways provide that cars do not.

Figure out how to get trains to operate everywhere instead of only on fixed routes, and then this comparison will be valid. Until then you're talking about two (more, really) different use cases with a minimal amount of overlap.

So at the very least we will need buses, and a lot of them, to feed the areas where it't uneconomical or otherwise unfeasible to run rails. Do the environmental math on that -- how full does a bus need to be before the pollution per passenger is better than a compact car with one passenger? How about a compact car with four passengers? Public transit would need a fundamental change in approach.

And of course this is only talking about people. Always lost in this conversation is that moving humans from place to place is just one use case.

> You can solve almost all of those problems more easily by improving road design with knowledge we already have.

Sure, to some extent. The knowledge we already have about how to prevent e.g. cars killing children, pedestrians, and cyclists is that you slow them down (and separate them which also typically involves taking space from cars to make room). But as seen above in this thread, that kind of thing meets opposition from people who say you're "making good things in life shittier".

> the areas where it't uneconomical or otherwise unfeasible to run rails.

If you've never done this, I suggest taking a look at old maps of the US's passenger rail network. We had a lot more rail in the past than we do now.

> improving road design with knowledge we already have.

Smaller roads with fewer lanes and lower speeds are very unpopular among car enthusiasts.

> Figure out how to get trains to operate everywhere instead of only on fixed routes

Cars can't operate everywhere so this is a unrealistic requirement in the first place.

> Do the environmental math on that -- how full does a bus need to be before the pollution per passenger is better than a compact car with one passenger? How about a compact car with four passengers?

Assuming a 1 person/car with a average 19mpg, and a average bus 6.2mpg, you need 3.06 people on a bus before it breaks even.

If you can have 4 people on a compact car with four passengers, you can have a bus with 3 people on it.

The fixed costs of public transport options, given the significant investment of public money that they tend to represent, are not zero either. The marginal cost of a journey is far more salient to whether a given option is preferable to any given person. Traffic jams are an extremely variable issue and I would argue are directly analogous to being crammed onto a delayed train with a thousand other people who can barely move - that is, essentially a rush hour problem that is more about throughput and the madness of commuting than it is about any particular specific form of transport.

Also note that your other examples violate my overarching point which is that they're about externalities. They don't represent advantages to the users' near term needs/desires, and in the case of my personal feelings about cyclists are actively in opposition, so they're almost always going to be fighting an uphill battle for mass acceptance.

> Traffic jams are an extremely variable issue

Variable? A single line of rail moves more people per hour that 6 lanes of highway - that's just physics.

Average speed of London traffic is 10 km/h while the new Elizabeth Line wooshes past at 90 km/h. It can cross London before your car gets 1/3 of the way.

A crowded train still moves at 90 km/h. Your car in a jam is personally comfortable (unless you need to take a piss), but doesnt move anywhere.

The idea that cars are comparable to public transport in situations of gridlock is preposterous.