Reply #8: How about taking the cars off the road?

[Lydia Leftcoast]

I bet that would get rid of more smog than shutting down every factory within 50 miles of Beijing.

Tokyo used to have a horrible smog problem, although it was largely gone when I arrived in 1977. After I noticed that the taxis run on propane, a driver told me that the city government mandated it after they noticed that the skies always cleared up on national holidays. Tokyo not only requires taxis and buses to run on propane but also continues extending its transit lines.