IIRC Paris has done something that in the past - you could only drive in the city on certain days depending on the registration of your car (even vs odd numbers).

And with great results: https://www.washingtonpost.com/climate-solutions/2025/04/12/..., https://news.ycombinator.com/item?id=43665793

But it was just a step towards more banning, which had great result (less traffic, more people circulating on foot, less pollution)

And people with multiple cars, multiple registration years, or maybe just people with means, will be the most affected.

Still happens every time air pollution gets too high.