This is not new technology. It's been around as long as cars have been around. If it were a better idea, it would have been done already.
Your comment reminds me of a comment made by Charles H. Duell, the Commissioner of the U.S. Office of Patents in 1899. "Everything that can be invented has been invented."
Here are some other interesting quotes from the past:
"Drill for oil? You mean drill into the ground to try and find oil? You're crazy." -- Drillers who Edwin L. Drake tried to enlist to his project to drill for oil in 1859.
"Stocks have reached what looks like a permanently high plateau." -- Irving Fisher, Professor of Economics, Yale University, 1929.
"Airplanes are interesting toys but of no military value." -- Marechal Ferdinand Foch, Professor of Strategy, Ecole Superieure de Guerre.
"Heavier-than-air flying machines are impossible." -- Lord Kelvin, president, Royal Society, 1895.
"This 'telephone' has too many shortcomings to be seriously considered as a means of communication. The device is inherently of no value to us." -- Western Union internal memo, 1876.
AFA the operating costs of CNG vehicles? If you choose to check out the link, you can find some details there. AFA compressed air hybrids, I don't have info on it. Remember, I posted an article from the Daily Mail yesterday, which I found interesting. I am not an engineer, nor am I a marketer for Peugeot, merely someone who is frugal, looking for ways to save money. A compressed air hybrid makes sense, as long as the savings outweight the amortized capital cost of the system. Peugeot feels it does. More power to them. Unlike electric hybrids, these will not have to overcome 600-1,000 of batteries using toxic chemicals and exotic materials, so should not cost anywhere near what electronic hybrids will cost.