Here is the best I can find on the clean air standards. I think pushing taxi companies to use hybrids, all electric, natural gas vehicles, etc. http://www.sfmta

Here is the best I can find on the clean air standards. I think pushing taxi companies to use hybrids, all electric, natural gas vehicles, etc. http://www.sfmta.com/about-sfmta/blog/sf%E2%80%99s-taxis-can-help-you-go-green http://www.sfmta.com/about-sfmta/blog/sf%E2%80%99s-taxis-can...