On my commute home a few weeks back I was sitting next to the CEO of Laclede Gas in St. Louis. I asked him why CNG wasn't being explored more as it's already used in a number of fleet vehicle applications. It's also cheap, low emission and widely used in other applications.

His response: It's hard to compete when only honda and a couple others are producing a CNG vehicle. He's also convinced that oil companies are doing a pretty good job keeping it down.