A taxi driver in Mumbai, India.

Four years ago, the smog in Mumbai was so bad that walking around burned my eyes and wiping my face with a white handkerchief harvested a black crop of ash and dust after a couple of passes across my brow. According to my former student, now professional advertising photographer Amogh Thakur, two years ago the city mandated that all public transport be run on Compressed Natural Gas (CNG). Walking the city streets this morning, it feels like an entirely different city. Breathing the air is no longer a tactile experience, and my white handkerchief harvests only sweat and the occasional patch of dust that has settled on my skin. To see what this greening looked like in practice, I followed a line of cabs waiting to fill up on CNG. The stations footprint took up no more than any filling station in the USA, and the filling time itself was about as fast as filling a large tank of petroleum.  Long live the yellow top fiats that so define this city!