The crumple zone is the area of a car that absorbs energy upon impact. It's designed that way. Engineers deliberately place weak spots in a car's structure to enable the metal work to collapse in a controlled manner. Since the collapse is controlled, energy from the impact can be directed away from the passenger area, and channeled to the floor, bulkhead, roof, or hood, for example. Energy from the impact is also used up in the deforming of the metal, often converting into heat and sound (loud noise).
The laws of physics say that an object in motion will stay in motion, with the same speed and direction, unless it is acted upon by an outside force. So if you are traveling at 60 MPH and your car hits a solid wall and comes to an immediate stop, your body will continue going at 60 MPH until it is stopped by, say, a seatbelt, airbag, or, at worst, a windshield. If the car has a rigid body, the rapid deceleration caused by the impact will produce injuries and fatalities. Because the stopping time is only a split second, the force on the passengers is very high.
However, cars with crumple zones act more like springs being compressed against the wall, resulting in a cushioning effect, slowing the time it takes for the car to come to a complete stop, and spreading the force over a longer period of time, with less potential for injury. As the car strikes the wall, the front crushes together like an accordion, absorbing the impact and allowing the middle and rear of the car to continue in motion for a short time. By making the time of impact one-tenth of a second longer, engineers can help make the crash have 20 times less force.
Almost everyone goes a few miles over the speed limit when driving, but recent studies indicate that even a small increase over the legal limit can greatly increase the risks of an accident. Using data from actual road crashes, scientists at the University of Adelaide in Australia found that the risk of a car crash hospitalizing or killing people doubled for every 5 km/h above 60 km/h. So a car traveling at 65 km/h was twice as likely to be involved in a serious or fatal crash, while one traveling at 70 km/h had a risk four times as high. Part of the reason is that a driver has less time to react. On average, drivers react in 1.5 seconds; one who is drunk or distracted by loud music or talking on a cell phone may take as long as 3 seconds to react. And the faster one is traveling, the less time one has to react to a perceived danger.