LPG?

[ozonehostile]

I wouldn't say it's any more of a bomb in your boot than a petrol tank...

lpg is more explosive than petrol so thats the main reason for insurance increases, also a petrol tank is designed to be enclosed within the floorpan of the car in a place that it sunlikely to be ruptured in a collision while an lpg conversion is aftermarket with a tank put either behind the rear bumper or in the boot, an area likely to be heavily damaged from a rearend collision.