[sveur (OP)]

How much space does the LPG containers take in a car, and is it more dangerous to crash with gas canisters in your car than if it was a regular petrol car?

[Karsten]

This is difficult to answer. How much space the container requires depends entirely on how big the container is or should be. That is up to you.

Safety? Depends on many things. I would assume that it is more the connections that matter than the tank itself. If the tank is hefty enough to survive a crash you still have to worry about the lines, valves, etc.. I would design it in a way that allows the pressurized bottle to disconnect safely and shut off in case of an accident. I wonder if earthquake prone areas have building codes that require such technology already. Make sure the containers are attached well; you don't want to get killed by the steel container crashing into the back of your head after you hit the wall.

[LeeE]

The LPG cylinders I've seen in LPG cars have been about one foot (30cm) diameter and eighteen inches (45cm) to two foot (60cm) high.  These cylinders have integral valves (they look like ball-valves to me) and the pressure inside the cylinder forces the valve closed unless it's mechanically depressed by the attachment tap.  They could therefore be dangerous if the tap is damaged in such a way that the ball remains depressed but the rest of the tap above it is sheared off.  I strongly suspect though that the taps are designed so that if the tap valve is damaged or removed, the depressing plunger is released, allowing the cylinder valve to close.

LPG cylinders are much more strongly constructed than a normal petrol tank, not just to withstand the pressure of the gas within but specifically to withstand damage.  If a normal petrol tank is damaged the petrol will only leave under the force of gravity but the release of pressurised gas is a lot more serious as you'll end up with a lot more, a lot quicker.  I'd expect the gas cylinders to withstand crashes pretty well and certainly better than a petrol tank.