London, where I live, has both congestion charging and emissions charging (ULEZ) but still has loads of traffic. I'd estimate about 75% of it is not private vehicles outside rush hour, and probably no more than 50% private during rush hour, in central areas. My estimates come from riding through it by motorcycle daily.
It's already been successfully done, there is just a lack of political will to make such measures permanent.
Ride 100 provides an excellent demonstration of this even just by closing -some- roads for -one- day.
cf this graph of pollution on Putney High Street:
I expect there are some people who do make other arrangements and take a bus, so it's a net gain, but there are also those who take their car on Monday since they couldn't on Sunday.
EDIT: I looked up how RideLondon works, map at the end of this PDF shows road closures https://d1ffaecguugkl4.cloudfront.net/ridelondon/live/upload...
So it's not even time-shifting necessarily. People can drive around that and just move the pollution from one street to the next. But yes, the pollution measurements on one of the closed roads would look better that day.
Yes, I know, it was an illustration of how much pollution is caused by traffic in London and how much could be gained by reducing those traffic levels overall. I am baffled that this is causing confusion to people.
My own commute times nearly doubled with the Olympic lanes. It would have been intolerable permanently.
BTW, pedestrian zones exist in most cities. The stores there still get their goods delivered and emergency vehicles still have access. Turning most of a city in a pedestrian/cyclist zone doesn't mean that you can't have any car traffic at all.
Eliminate 70% of that traffic, and something will break. Kill taxis and business will suffer. Kill trade vans and basic utilities will be out of action for longer. Kill deliveries and the pace of economic activity will slow down. Deliveries are the best candidate for reduction, but don't forget use of delivery vans is directly related to public transport use - people who use public transport can't carry lots of stuff around, or trek out to centralized pickup hubs, so they need delivery vans instead.
Cars aren't necessary, of course; we could get by with horses and carts. But removing them would not "vastly improve" quality of life.
I live in Greater London, about 12 miles from where I work (35 minutes by scooter, 55 minutes by public transport if you time it perfectly, average 1h20 if you don't). My preferred supermarket is 3.9 miles away by road, about 40 minutes by bus or 12 minutes by car (though I normally go by scooter). Would my life be better without a motorised vehicle? My opinion is it definitely would not!
Either I'd need to severely reduce my choices in purchasing or commit to spending significantly more of my life on and waiting for public transport. Neither of these would vastly improve my quality of life.
Largely because public transport is underfunded in London and, of course, ridiculously hampered by the car traffic.
Try getting a bus down the A2 in peak hours or at the weekend. It's often quicker to walk. That's why people end up getting cars and ... making things worse for everyone.
From direct experience: food delivery works well enough for branded, processed and other long shelf life products. It's not bad for meat, as long as you're ordering from a specialist and not a supermarket (and of course there is a price premium). It's not good at all for fruit or vegetables, with current suppliers. Goods are bruised, mouldy, unripe, overripe, etc. It's also useless for bread; you always get yesterday's bread.
I know of families in ecotowns that don't have cars. The tram service covers nearly everything they need, and when they do actually need a car, they get a car-share/rental.
The infrastructure where they live is set up for this, to the extent that owning a car is awkward, because you're not allowed to park it anywhere near the houses, but it's fine because there are such good facilities for people without cars in that area.
The point is that we need cars because we don't have good facilities for not having cars, and we don't have good facilities because we all have cars.
I still use public transport as much as I can, and the traffic in London is such that it's often a viable option, but a car is also a necessity.
I think you're over-interpreting your parent. In some cities it is feasible to go without cars. There's a lot of space between cities and a lot of smaller cities and towns where that isn't feasible, at least not currently or without a lot of additional infrastructure.