correct me if I'm wrong: I think CNG taxis are still more environmentally friendy than euro 4 or 5 diesel taxis as I find that less exhaust fumes are emitted from CNG taxis. I think its time to import more environmentally friendy vehicles, and not limited to taxis only, as I find the roads nowadays are quite polluted. Also, our govt should discourage the use of old vehicles and introduce regulations to get them scrapped asap, as they generally are very pollutive and emit lots of smelly and harmful smoke.