World cities with ambitious plans to tackle air pollution
California leads US states towards cleaner air
San Francisco plans to ban all cars from Market Street, a main thoroughfare through the city, by 2020. Under the proposals, mass transit schemes will be more easily accessible. The area will also be made more bike and pedestrian-friendly. The US state of California is one of several states, cities and countries planning an all-out ban on fossil-fuel vehicles within the next 25 years.