Just as dangerous is when the car gets rear-ended. Have you seen the videos of cars being hit with kids in the back? The acceleration sends the passive mass of the child out through the back window where they get crushed between the two vehicles on the rebound.
I haven't, but I can imagine it happening.
Let's face it, an unsecured child in the car could go anywhere in the case of a major collision. Most people these days seem to obey the law and strap 'em in, but the odd idiot doesn't.
Another crazy thing I saw was two children standing with their upper bodies sticking out of the open sunroof of a car doing about 80 mph down a motorway!
Mind you, compared to this...
[media]
]View: http://www.youtube.com/watch?v=8SqD8FWB6o4[/media]
Flippin' heck!
