[pjc50]

I don't understand what the security implications might be? It's just the normal gas that's available from mains gas everywhere, in a low-pressure tank. Probably no more dangerous than existing CNG/LPG vehicles.

[kwhitefoot]

Much less dangerous as the pressure is very low and the quantity of gas very small.

[toomanybeersies]

LPG is usually stored in a sturdy metal tank, and not a big balloon.

[aphrax]

LPG can be pretty dangerous in a car when not installed properly…