I think that you have got the idea that there is already a number of ways to avoid having to have fueling stations in order to have access to LPG or CNG on the highways. That really isn't the problem. The problem is a matter of safety of the conversions.
This is where government should step in and mandate three to five standards that get to compete for the brass ring in the marketplace. Most people would like to believe that no one would install a faulty LPG or CNG fuel system in their converted hybrid. I also would like to think that people don't make mistakes and that some mistakes can be come habitual with high demand and low standards. Garage fueling and backyard conversions are fine for the enthusists but the fact is that there are vehicle on the road that are twenty plus years old and the idea that the owners will be giving them up soon is a little hard to comprehend given today's finances. So, can you say explosion?
Let's take this down to the base level. Yes, I would be willing to convert my 1988 Buick Century with 390K miles on that chassie, would you be willing to back that warranty on your back yard conversion for say, $1 a mile liability? That's $390,000 in liability for each install minimum. You can say ouch now. It's a rational risk mitigation strategy that comes with the territory.
Mickey
Your 20 year old car is so dirty that it should be taken off the road. We could probably make two little ones out of an old Buick. Vehicle weight is the main reason we should be replacing everything. Those little Smart cars are a bit extreme but because they are made of titanium they get good mileage and have the best crash test numbers on the road - except from the rear.
All I know about CNG is when I take state owned taxi's in India and they have to refuel, I'm forced to get out of the car and step several feet back in case of an explosion!
I've always been a fan of cars that pass everything except gas stations. I would love to be able to continue to drive my car of choice and not perpetuate the foreign oil dependence problems we have today.
I really hope that energy independence doesn't limit the marketplace to small and ugly cars.