During a motor vehicle crash, three collisions happen:
The Vehicle Collision. This is what happens at the point of impact, whether it comes from the front, back or side. The vehicle begins stopping as soon as it collides with an object such as another vehicle, wall or tree.

The Human Collision. At the moment of impact (whether you are driving or not), you will be moving at the same speed as the car. If you are unbelted, whatever is in front of you (ie. steering wheel, windshield, front seat, another person, etc.) will stop you from moving. The human collision is the one that causes injury.

The Human Body’s Internal Collision. Even after you have come to a complete stop, your internal organs continue moving forward. Suddenly, these organs collide with other organs. This collision can cause considerable and potentially fatal injury.