The Oil Drum

Not sure Propane is that easy to store: yes it liquifies under moderate pressure at ambient temperatures, but in large quantities that's an expensive tank relative to unpressurized tanks for liquid fuels, or cavern storage of LNG.  

OTOH, storing a moderate amount of propane as a liquid in a pressurized tank in a vehicle seems to me as a better way to go than pressurized (but still gaseous) methane.  Why is that not done as often?  Perhaps because methane has a price advantage over gasoline, while propane does not.

Talking about price, from what I've read, a large part of the propane supply (in the USA) is as a byproduct of the refining of oil, which may explain why its price is unlinked from that of NG, and tracks oil fairly well, despite NG "liquids" being the other source of much propane.  As usual, the price is determined by the marginal, most expensive, source.