I am among the first private owners of a CNG (Compressed Natural Gas) car in Singapore. There a just a few hundred around (not inc taxis).
After considering and rejecting an electrical Hybrid, I bought my Toyota Axio in December 2008 and got it converted to a bi-fuel vehicle.
Why bother you ask?
Well let's "weigh" the situation. The heavy cylinder seems like I am always carrying a corpse in my trunk which takes up half of my trunk space. Performance is slightly affected but then again I never floor the accelerator when the lights turn green. I outgrew that phase pretty quickly when I had to pay for my own gasoline. Another pain --- just 3 CNG stations in Singapore and none on the East where I live. The Oil companies said they would but then again they ARE oil companies and I should have known better.
Now for the good part, CNG burns cleaner, is much cheaper and the government subsidised my installation. Ok, there is another reason -- I enjoy being different and people approach me when they see my CNG sticker to ask me about it.
If I was a full fledge greenie, I would travel by public transport. But I value the quality of life too much to give up my car addiction. I am very happy with the compromise. I played my part for the environment and it was the right thing to do.