The piling up of air pollution in many cities and urban areas due to worldwide traffic chokes on millions of roads in many cities is still given official prioritaires or even promoted by legal actions. Air quality in many cities and urban areas around the world is becoming major health threats for everyone. Collective breathing of rubbish in the air of many cities is now much more serious than individual smoking, this is making living in cities a nightmare especially where thermal isolation is non-existing. In hot and arid climate zones with limited or no rain, poor air quality makes such health threat a chronical problem and daily struggle for survival. It is not only because of cars but also the failing and collapsing old infra-structures of aging transport systems not suitable for modern life. Many sources of pollution other than chemical ones, e.g. physical and biological, from factories, population and household in heavily populated areas with daily traffic (in and out) from rural areas add even more pollution to the emittions from traffic.

Even in some parts of the world cultural and social issues screen and shut out half of the population from promoting sustainable solutions in mitigating and counteracting the core roots of air pollution. Even more serious is where the whole population have no alternatives other than joining the heavy traffic and collapsing infra-structures thus removing all little ramaining possibilities to breath whatever left to breath. Even those who wish to walk can hardly find some safe, free and secure space to do so. 

https://www.theguardian.com/cities/2017/jun/12/girls-ride-bikes-iranian-women-defy-cycling-fatwa-tehran?CMP=share_btn_fb