I've even seem children on the knee of parents in the front seats...[/quote]

That really really gets my goat - and the adults are always wearing their belts but the kids are loose.
In my previous life as a Met Police Officer I regularly pulled over cars in West London with that set up - five adults with seatbelts on and a load of kids thrown in on top loose.
My opening line was frequently "Do you love your children?" Harsh but to the point - 30mph and the kids will be straight out the windscreen.

Some people just do not engage their brains in cars

caz