Physics of Auto Accidents and the Safety Devices Used to Prevent Accident Injuries

August 8, 2012

Auto Accidents

Car accident safety devicesIn the early 1950s, Dr. C. Hunter Shelden made a major contribution to the automotive industry with his idea of retractable seat belts. Dr. Shelden had a neurological practice at Huntington Memorial Hospital in Pasadena, California and was seeing a high number of traumatic brain injuries from auto accidents coming through the emergency room. He began analyzing seat belts being used at the time and the related injuries and deaths from auto accidents. His findings were published in the November 5, 1955 Journal of the American Medical Association (JAMA) in which he proposed not only retractable seat belts, but also recessed steering wheels, reinforced roofs, roll bars, door locks and passive restraints such as the air bag. Subsequently in 1959, the United States Congress passed legislation requiring all automobiles to comply with certain safety standards. (1)

The task of a seatbelt is to stop the occupants of the automobile when it stops. Without a seatbelt, the forces of a car accident would result in stopping distances for occupants to be approximately 4 or 5 times greater. With no seatbelt to stop the occupants in the car, they fly free until stopped by impact of something within the vehicle such as the steering column or windshield. They are also susceptible to being ejected from the vehicle which often results in extremely serious or fatal injuries.

Stopping distance with a seatbelt is estimated to be about one fifth of what it would be without, causing the average impact force to be about five times as great. The work done to stop an occupant of a car is a mathematical calculation. It is equal to the average impact force on the occupant times the distance traveled in stopping. (2)

From 2004 to 2008, seat belts saved over 75,000 lives nationwide — enough people to fill a large sports arena. During a car crash, being buckled up helps keep you safe and secure inside your vehicle. Seat belts reduce serious crash-related injuries and deaths by about 50%. (3)

An airbag is another vehicle safetydevice. It is an occupant restraint system consisting of a flexible envelope designed to inflate rapidly during an auto collision. Its purpose is to cushion occupants during a car crash and provide protection to their bodies when they strike interior objects such as the steering wheel or a window. Modern vehicles may contain multiple airbags in various side and frontal locations of the passenger seating positions, and sensors may deploy one or more airbags in an impact zone at variable rates based on the type and severity of impact; the airbag is designed to only inflate in moderate to severe frontal crashes.

Airbags are designed with the intention of supplementing the protection of an occupant who is correctly restrained with a seatbelt. Most designs are inflated through pyrotechnic means and can only be operated once.

The first commercial airbag designs were introduced in passenger automobiles during the 1970s with limited success. Broad commercial adoption of airbags occurred in many markets during the late 1980s and early 1990s with a driver airbag, and a front passenger airbag as well on some cars; and many modern vehicles now include four or more units. (4) According to the National Highway Traffic Safety Administration, an estimated 4,758 people are alive today because of their air bags. (5)

The combination lap/shoulder safety belts and air bags is the most effective safety system available for occupants of motor vehicles, and it is 75 percent effective in preventing serious head injuries and 66 percent effective in preventing serious chest injuries.

If you or a loved one has become the victim of an auto accident anywhere in Ohio, contact the Ohio law firm of Slater & Zurz LLP for a free consultation to discuss your options for recovering compensation for the injuries and damages sustained in a car accident. Please call 1-800-297-9191 or send us a message from our website at


1.  C. Hunter Shelden, M.D., (November 5, 1955). “Prevention, the only cure for heat injuries resulting from automobile accidents”. Journal of the American Medical Association.

2. Hyper Physics, copyright 2012 C.R. Nave, GeorgiaStateUniversity

3. National Highway Traffic Safety Administration

4. Wikipedia

5. National Highway Traffic Safety Administration or NHTSA.

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About slaterzurz

Slater & Zurz LLP is an Ohio law firm of highly experienced and respected attorneys. Over the last 40 years, we have developed a reputation for getting positive results for clients. We've been trusted with handling over 20,000 personal injury cases and our clients have received more than $120,000,000.

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