Many cities in Europe have introduced climate zones in the past ~20 years, mainly to ban older smoky diesels like that. Petrol cars have also gotten more efficient; smaller engines (1 liter 3 cylinder ones are the norm now for smaller cars), smaller cars, more efficient engines, stop/start systems, hybrids and EVs (especially good for city traffic), etc.

That said, when I was in Paris last there were a lot of motor-scooters; while they also have small engines etc, I can't see them being much cleaner than well-designed cars, only due to their smaller size. Given time, I'm sure the range on their electric counterparts will become good enough as well to become a practical replacement.