If you hit the windshield with your head, the stopping power is concentrated on one of the most vulnerable parts of your body. It also stops you very quickly, since the glass is a hard surface. This can easily kill or severely injure a person. A seatbelt applies the stopping force to more durable parts of the body over a longer period of time. ("How Seatbelts Work", 2). .
Airbags are another type of safety devices that were first invented during World War II and appeared in automobiles in 1980s. ("How Airbags Work, 1") "Since model year 1998, all new cars have been required to have air bags on both driver and passenger sides." ("How Airbags Work, 1") There are three parts to an airbag to make it work: first, airbag itself is made of a thin, nylon fabric, which is folded into the steering wheel or dashboard or, more recently, the seat or door, second, the sensor detects if a crash occurred, and third, sensor tells the airbag ignition system that a crash occurred and it reacts sodium azide (NaN3) with potassium nitrate (KNO3) to produce nitrogen gas which fills up the airbag faster than a blink of an eye.
Another important side of automobile safety is how it grips to the road. This includes tires, brakes and suspensions. Car tires are being improved all the time. Tire safety is based on many factors: how it acts on dry and wet roads, snow, or deep water puddles. Last two are most important when choosing tires, because most tires are pretty similar in first two categories. Aquaplaning is a dangerous thing in driving that can be even more dangerous than driving on ice. Aqua planning is basically water forcing the car lift off the road and it is critical to have tires that have special threads to prevent that lifting.
Brakes are another important part of the car. Most car manufacturers switch from drum to more effective disk brakes to improve the safety.
Ventilated brakes are made to reduce the temperature of the brake disks to prevent their damage.