What happened to propane and CNG

[cjperformance]

Over here, Australia (south australia) we are currently paying around $1.50(varies by .25c/L either way on a regular basis)/Liter for our 91 ron base grade crap.
We pay around $0.69 /$0.90 / L for LPG.
On the average 6 cylinder family car here you could expect aprox 13L/100km around town on petrol/gasoline and around 18L/100km on LPG , its still worthwhile on these vehicles. It depends greatly vehicle to vehicle of course but in most cases here "daily" running costs are still cheaper disregarding conversion costs etc.

[GARY C]

These fuels may still be popular in other regions but I haven't seen much use since the 90's. Has fuel injection negated the economy of converting or purchasing a CNG vehicle?

After 20 years I asked my Propane guy why he uses a diesel trucks for his Propane business, his reply, "Less problems and they last longer"

There just hasn't been as much development surrounding that need. I think there should be it's probably the best and most under used alternative fuel.