No, I have a better idea.
Replace standard insurance with...
ROADKILL WINS PRIZES
It's easy. You have a point calculator added to your car. Points are awarded every time you manage to successfully eliminate a selfish, annoying, arrogant and/or dangerous person from the roads.
The scoring system is set out in levels with 1 point for eliminating a cyclist who can't keep to the left, 2 points for boy racers who give the rest of us a bad reputation, 3 points for people who shouldn't or don't have a driving license, 4 points for people who can't drive on motorways and either hog the middle lane at 40mph or sit in the outside lane because they think it's the BMW lane and 5 points for scum who fail to look after their cars and have no brake lights, headlights or indicators working and all four tyres bald, with no MoT or insurance.
Points can be traded in for armour and weapons to upgrade your car - 20 points gets you spiked armoured body panels, whereas 50 will get you a bonnet mounted minigun. Larger scores such as 100 points can be traded in for exotic Carribean holidays.
I think it's a winner.