Car accident forces explained

Last blog we talked about different types of car accidents and how everything inside the car travels towards the point of impact. We’ve gone through three different points of impact (front-, rear- and side impact) and explained why car seats and especially rear faced car seats are most effective.

At the end of that article we briefly showed you how much force is needed to prevent you or your little one from moving towards the point of impact. It’s very important everything inside a car stays as still as possible during a crash in order to best prevent injuries. 

law of motion explained

The example described before was as follows:

The weight of the moving object multiplied by the speed it’s travelling at is the restraining force that is required to keep a person in place and prevent it from hitting other objects in the car. Let’s say your child weighs 15 kg and you are travelling at 30 km/hr. Then a force of 15 x 30 = 450 kg is needed to prevent your child from flying through the car. This 450 kg force will be exerted through seat belts and the 5-point harness of the car seat.

450 kg is a lot of force that needs to be distributed over the fragile body of a baby. This amount of force needs to be spread out well across specific points in your baby’s body in order to prevent serious injury. By using the car seat’s 5-point harness, as opposed to the car’s 3-point seat belt, the entire restraining force can be divided more evenly over the child’s young body, reducing the amount of stress on each point.

Moreover, the baby’s most rigid body parts (shoulders and hips/pelvis bone) can withstand the high load forces of a crash better than the soft body parts (lower abdomen). With a 5-point harness the baby’s soft abdomen area is better protected.

In addition, have you ever seen the aftermath of a car crash? A lot of stuff that was originally inside the car is ejected through windows that break during the accident. A 5-point harness ensures that the child is better secured and stays in the safest position possible: within the protective shell of the car seat.

5-point harness of Britax car seat Little boy in Dualfix car seat

For this reason Britax always advises to use a 5-point harness for as long as your child fits in one.

What you absolutely shouldn’t do, is to keep any child, no matter how big or small, in your lap and not wear a seatbelt yourself. Because the same physics we described earlier also apply to you. Let’s say you weigh 60 kg and you are travelling with 30 km/hr, then that means you turn into a 1800 kg (60x30) force. Since there’s no seatbelt to hold you back, you will hit whatever is in front of you and use your baby as a pillow to soften the blow.

Restraint systems in vehicles have been developed, studied, improved and mandated a lot throughout history worldwide. They are effective, so let’s make good use of them. Human life is invaluable.

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