The trouble with all of these sort of things is that 99% think they are an excellent driver and whilst other people might drive like maniacs and use their cars as a weapon, they personally are above reproach AND they'd never swing a baseball bat at someone, what a stupid thing to accuse them of doing. *eyes glazed over, mental shutters crashed into place*
The other 1% are the couldn't give a **** idiots who won't be reached no matter what you do.
The child running in the road and the think motorbike (pet niggle there) campaigns work because car drivers can rationalise them as other peoples stupidity on the roads not theirs. If the child had looked properly....... if the motorbike was a bit further out or was going slower or.........
As soon as you say to someone, your car is a weapon capable of killing, you've lost them:
1) You're 'getting at' them and their driving skills.
2) They keep getting told cars are super safe now, they get NCAP safety ratings and brilliant tyres and ABS brakes and crumple zones and air bags rammed down their throats by advertising. With all this how can cars possibly be as dangerous as they used to be? What they don't get given is the message that all of these features are only making them safer for the people inside.
3) Mechanically and electronically cars are far better damped and soundproofed now. They sit far more stable on the road and don't get buffeted about, you can't hear the air whistling past them like you used to, particularly not wth the radio at 11 or the ipod pludgged in. External air displacement and turbulence isn't something that impinges on a drivers sensibilities.
4) Unless they've cycled in traffic, They are unable to put everything together and make the emotional correlation between a 6 inch pass at 37mph on a wet day and swinging a baseball bat at someone's head.
My campaign would not tell them that they're the problem, it would be to be to remind then how vulnerable they can be made to feel by much bigger and heavier objects treating them without respect.
Make it something that they can connect to with them in the victim role, then show them how to be the hero.
Family in car, they've pulled into the kerb checking a map/reprogramming the sat nav. They're sat there in silence with stuff roaring past and shaking the car about, you see a shot of the rear view mirror with an artic lorry hurtling towards them, they're all looking back, horrified expressions, heart in the mouth moment as it swerves round at the last minute and the whole car goes dark and really rattles about, some sunglasses fall off the dashboard, can of coke fizzes over etc. Driver (dad) asks if everyone is all right, wide eyes, ashen faces, silent nods as they carry on. Then cut away to the preachy bit: a close pass by the same family on a cyclist, they look back as s/he's correcting a big wobble and someone in the car says 'Crikey Dad you're just like those lorries were on us, give the poor guy a bit of room eh'. Reset the scene, this time a good pass, car waits throught a traffic calming island, then passes well to the centre white line, cyclist unperturbed, same voice from the car, 'that's more like it dad, nice one'.