Too many children, not enough car

There was a discussion on one of the forums that I frequent about what to do when you have more children than room in the car.  I blanched reading some of the responses, which included (a) double buckling or (b) sitting a child or adult on the floor in between the front seats.
And this was considered good advice.

It is not good advice.
It is very, very, very bad advice, and will get you traffic tickets and fined at best, and at worst, will kill someone in your family.

Here is why:
People in car accidents get hurt when their bodies strike something else, such as the dashboard, steering wheel, seat in front of them, door, or another person.  Double buckling puts two children far too close together and constrains them.  Their bodies are trying to occupy the same space.  In a crash, those children are going to go into each other at a high rate of speed, most likely hitting their heads together.  This can and does cause serious injury, including brain damage and death.  This was tested in crash tests, and the two child size dummies buckled together in a relatively low speed impact struck each other hard enough to cause severe injuries. 

 A child should never be buckled onto an adult's lap as well, because the child could be crushed by the magnified force of the adult in an accident.  I'm not kidding--at a mere 30 mph, the force of a 150-lb adult in a crash is over one ton.  You may be thinking that there is nothing for your child to be crushed into, especially if you are sitting in a row seat in a minivan or in the back seat of a car.  Crash tests, however, have proven that the massive force of an adult or older child pushing the small child on the lap into the seat belt is enough to cause death.  To put it otherwise, the force alone of the adult pushing the smaller child against the seatbelt is enough to crush that child's internal organs and cause death.

The same reasoning goes for why unrestrained passengers should never be allowed to ride in a car, whether it is in a seat or on the floor.  The magnified force and the speed at which that person will travel in an accident is great.  A child sitting on the floor up front between the seats risks flying into the dashboard, out of the car through the winshield, or into the side doors in something like a minivan.   Some of the likely injuries?  Brain injuries, broken ribs, punctured lungs, spinal cord injuries, lacerated internal organs.  And those are just the likely injuries.  A unrestrained passenger is also likely to fly into someone else in an accident, particularly a restrained passenger, causing them injuries as well.

So what do you do?  Preferably, you take two vehicles or upgrade to a vehicle large enough to accomodate all the children.  I understand those larger vehicles are more expensive, but I am pretty blunt, and if you can't afford a larger car to ensure your children's safety, you need to stop having children.  If worse comes to worse and you find yourself in a situation where y0u must travel and don't have enough room in the back, the largest child should be placed up front and the seat moved back as far as possible.  If you can turn off the front passenger airbags, do so.  In no case should a child in a safety seat ever be placed in a front seat. 

For more information, check out these sites:
Safety research
Car seat safety