Catastrophic Injuries and the Physics of a Car Accident

Categories: Accidents

It is easy to see why automobile accidents cause so many injuries. Our bodies are made of soft tissue. Vehicles and the objects they collide with are made of steel, glass, concrete, and other hard substances. This makes us vulnerable during an impact. Bruises and cuts are common, as are strains, sprains, broken bones, and concussions. But what about more serious injuries, like ruptured organs and spinal cord damage? Are there other forces at work during an accident that explain these and other catastrophic injuries?

Engineering Mistakes of the Past

Early automotive designers assumed that a strong vehicle body was the best way to protect the vehicle’s occupants during a collision. “Crash resistance” was a matter of being sturdier than the other object involved, whether it was a tree, light pole, or another vehicle. Such thinking did not bode well for accident victims. Consider the following crash data from Detroit during the early days of automobiles and Orange County nearly a century later:

Detroit, 1917 Orange County, 2015
Fatal automobile crashes: 168 179
Automobiles on the road: 65,000 2,250,000

These two locations from different eras had close to the same number of fatal accidents in a one-year period, despite Orange County’s having a vastly greater number of cars on the road. Safety improved for a variety of reasons, one of which was a recognition that, as counterintuitive as it may seem, a less rigid vehicle provides more protection during a collision.

Vehicles that Crumple by Design

Stock car racers have an old saying that sums up how the laws of physics apply in a car crash: “It’s not how fast you’re going, it’s how fast you come to a stop.” These drivers understand that the more abruptly a vehicle comes to rest, the more force a person inside will experience. Sir Isaac Newton expressed it this way:

Force = Mass x Acceleration

To understand force as described in Newton’s equation, we must consider two factors – mass and acceleration. The mass of an automobile remains constant during a crash, so we can disregard that factor. As for acceleration (or deceleration in this case), we need to look at one more equation:

Acceleration = (Change in Velocity)(Time)

Acceleration, then, refers to the rate at which an object changes its speed and direction. The important thing to note in this equation is that time is the denominator. Thus, when we return to Newton’s equation, time will have an inverse relationship to force. The more time involved in a collision, the less force it will produce.

This is why modern vehicles are designed with “crumple zones.” Unlike their predecessors, newer cars are engineered to collapse inward in an accordion-like manner during a collision. The crumpling motion increases the time it takes for the vehicle to come to a rest after initial impact, thereby reducing the amount of force to the vehicle’s occupants.

The Human Body’s (Limited) Ability to Withstand Force

Even the most advanced safety features of today’s automobiles cannot protect us from all the force produced in a traffic accident. Some amount will be experienced by the occupants of the vehicle in every collision. When the force exceeds what the human body can handle, catastrophic injury can result.

Diffuse axonal injury (DAI), a type of traumatic brain injury, is one example. During a head-on collision, the deceleration force is so powerful that the brain shifts inside the skull. But it does not shift in one consistent motion. Individual parts of the brain have different densities relative to each other. As they shift laterally in response to the deceleration force, they do so at different rates, resulting in a shearing effect. The brain’s connective nerve fibers literally tear apart, leading to serious brain damage or death.

The human body can endure a lot. Theoretically, we could safely travel at an incredibly fast constant rate of speed, so long as we sped up and slowed down gradually enough. It is the sudden stopping motion that our bodies cannot withstand and that leads to catastrophic injury. Unfortunately, a sudden stopping motion is exactly what happens in most car accidents.

Neale & Fhima have been in the business of winning personal injury cases for a long time and chances are, they have handled a catastrophic injury similar to yours. We invite you to learn more about us, ask questions, gain insight and begin to forge a relationship that will help you through the difficult road ahead.