Kinetic Modeling of Seat Belt's Performance in Crashes

Impact with the interior of the vehicle and being ejected are the most common mechanisms of injury in car accidents. Based on reports, the use of seat belts reduces the probability of being killed by 40–50% for drivers and passengers in the front seat and by about 25% for passengers in the rear seats. Also investigations show that seat belts are most effective in frontal impacts and in running-off-the-road accidents where the probability of being ejected is high if seat belts are not used. We aimed in this paper to model and to compare the accidents both in restrained and unrestrained conditions, based on classic kinetics fundamentals. According to developed models, we can show the higher the speed of vehicle before the accident, the greater the applied impact to passengers. Also the more flexible the body of vehicle, the less the impact to passengers is. In the case of unrestrained passengers, the further the distance of passenger head to windshield, the greater the impact is. Of course arbitrarily getting close to windshield when accidents, is not the natural habit of passengers. For this reason to make passengers safe during crashes, they have to wear seat belts. Seat belts should effectively be able to stretch in accidents to a constant amount of force, F. This force should keep constant by the full stop of vehicle in accident. Modeling shows that the distance of front seat to windshield should be long enough, in the case of using seat belts. In fact seat belts should be designed in a manner that the force applied to passengers during the accident, remains constant.