>>3765956Nuclear cars?
The chart is about NOx pollution. No cars, no pollution. Paris achieved this by removing parking, closing off roads, and introducing a 30 kph speed limit everywhere else to discourage people attempting to drive into the city.
The problem with walk-only cities though is that people rarely like to walk for more than a quarter mile, especially when carrying stuff, so you need a dense network of metro and bus stops with more vehicles all around the clock. This reduces average ridership per vehicle, which makes the transit system less efficient and economically unsustainable on passengers fees alone. That means the government has to step in and subsidize the public transit system for the city folks using money they take from everywhere else - a highly regressive move.
The public transit costs money and introduces waiting times, and often impossible transit schedules switching from vehicle to vehicle for people attempting to travel in and out of the city, so it reduces all kinds of inbound traffic to the city centers and business starts dying. The people living in the city live off of trade, so they start to move out and get replaced by people living on government subsidies, which the property owners invite in to keep receiving rent somehow. Taxes on the remaining working people increase as the city starts losing revenue. In a couple decades, your city becomes downtown Detroit.
