The new elected major of Paris has a very ambitious plan that is published and explained on the website of Eric Britton (Lyon). His website can be found here.
This measure leads to less air pollution, less energy use thus less CO2 on the one hand and on the other hand the (inner) city becomes less attractive for cars. The noise will go down just a bit (hardly noticable) due to this speed reduction. We welcome this courageous mayor! Which city follows?