Evidence of the importance of wearing a seat belt while in a moving vehicle is not a recent discovery; many studies have been conducted to compare the hospital costs for victims of crashes that wore seat belts against those who did not wear them. In 2001, the National Safety Council revealed that the average inpatient costs for crash victims not wearing seat belts were 50% higher than victims who were wearing seat belts during the accident.
In 2002, the National Highway Traffic Safety Administration reported that the deaths and injuries that result from not wearing a seat belt cost an estimated $26 billion annually in medical care, lost productivity and other related costs.
Recently, the Minnesota Seat Belt Coalition has been conducting its own research to determine how the use of seat belts impacts the cost of health care. Using Minnesota vehicle crash records from 2002, the group has discovered that hospital costs for unrestrained crash victims were 94% higher than hospital costs for those using seat belts. They estimated that increasing seat belt usage in Minnesota to 94% from the current rate of 84% could reduce the cost of crash-related hospital care an average of $19 million annually over the next 10 years.
Many people might wonder how a simple piece of equipment could be so effective in reducing crash-related hospital costs, and potentially save their life. To understand how a seatbelt works, one must first examine a basic principle of physics called inertia.
Sir Isaac Newton is credited with refining the concept of inertia in his work entitled Laws of Motion. Newton’s first law stated that, “Every body perseveres in its state of being at rest or of moving uniformly straight ahead, except insofar as it is compelled to change its state by forces impressed.” Put simply, an object will continue to move in an straight line until something interferes with its path.
Take that basic premise and apply it to a moving vehicle, which contains a driver and passengers. If a vehicle is traveling at 40 miles per hour, inertia should keep it moving forward at this pace, undisturbed. However, other factors like air resistance and friction caused by the interaction of the tires and the road surface are continually slowing it down. The car’s engine is designed to compensate for this energy loss and keep the car in continuous motion.
Separately, everything inside the car has its own inertia. Even though the passengers’ inertia is separate from the car’s inertia, while the car is traveling at 40 miles per hour, the passengers are traveling at 40 miles per hour as well. At this point, both the car and the passengers have the same inertia.
If the car were to suddenly stop because it impacted with another object, the passengers’ inertia and the car’s inertia would be completely independent. The force of the impact would bring the car to an abrupt stop, but the passengers would still be traveling at 40 miles per hour. Without a seat belt, the inhabitants would continue to move forward at 40 miles per hour until their path was obstructed, usually by a steering wheel, dashboard, or windshield. Depending on where and how the passengers landed, they could be killed instantly, injured severely, or walk away from the crash unharmed.
The deciding factor in this equation is the seat belt. A seat belt applies the stopping force to the sturdier parts of the body over a longer period of time. If it is worn correctly, it will apply the major portion of the stopping force to the rib cage and the pelvis, which are better able to handle it than other body parts. The belts extend across a wide section of the body, so the force is not concentrated on a small section of the body and cannot do as much harm as the impact of an object in the car. In addition, the flexible seat belt material stretches to keep the stop from being too sudden.
This simple piece of equipment relies on the properties of physics to save both lives and millions of dollars in health care annually. It could save you money in taxes and health insurance costs. The three extra seconds it takes to reach over and fasten the belt seem insignificant when you consider the many benefits of wearing it. The next time you ride in a car, check to see if all the passengers are belted in; it could be the difference between life and death.