@DdraigGoch One way or the other, cars are the problem and the solution is to discourage them.
Exactly.
You have good ideas and they exist where I live. I live off a major road, which is also residential on either side with a mix of old, middle and young, and includes a small inpatient mental health hospital and sheltered accommodation for elderly and disabled people. There's also a well-attended church and community centre and some restaurants and pubs.
If you moved there now you'd know what the traffic was like but there is a large housing estate fronting the road which was built in the 1950s on a bombsite when the traffic was nothing like it is now. I imagine some of the older residents have been there from the Sixties and Seventies when the traffic was much calmer too so it's a nonsense to say people knew what they were getting into or that things shouldn't change to help them now that our knowledge of air pollution is much better.
As I said, I'm away from the main road which isn't as busy as the South Circular where that little girl Ella lived, but not far off it. My own street runs directly off it and is quiet but that's only because the council have installed measures to prevent rat-running. Otherwise we'd be plagued by it. We still get the air pollution, just not the noise, dirt and idiots who complain about having to drive at 20mph in residential streets as if it's infringing their freedom. Why shouldn't my council act on my behalf to make my life better just so someone can shave a bit of time off their journey or act in "freedom"?
That point brings me to "15 minute cities". I live in one but only realised it a few years ago when people started muttering about a shadowy cabal who wanted to control us. I just thought it was really good to be able to walk to doctors; dentists; schools (primary and one secondary); shops; restaurants and pubs; a public and private swimming pool; public and private gyms - there's even a cinema here now.
If I want to go further afield, I can by walking if I am feeling energetic or using public transport if not. It's as you said, I'm not banned from doing it - I can do anywhere in this country and even abroad on public transport, and why wouldn't anyone want that?
I actually used to work a 10-minute walk from home. I used to walk 35 minutes to another office. I could have got the bus in slightly less time but because of roadworks and traffic it was easier and much more pleasant to walk across the park giving my cardiovascular system and mental health a work out. Also I liked the ducks on the pond. I'd only get the bus if it was very rainy or cold. I was much fitter when I worked there and I didn't even have to try.