Did you know that first writings on head impacts came from the ancient Greeks? In a work written in 400 B.C.E and appropriately entitled ‘On Injuries of the Head’, Hippocrates (of Hippocratic oath fame) wrote about the bone of the head “behind the vertex and the ear”:
when exposed to the same or even greater injuries… the bone is less liable to be fractured and depressed than elsewhere… in a fatal accident the patient will live longer when the wound is in the posterior part of the head than when elsewhere.
The first systematic and scientific studies of trauma biomechanics were conducted by an anatomist (Otto Messerer) in the late 19th century and published as ‘On Elasticity and Strength of Human Bones.’
These were early explorations into the science of impact biomechanics: how injuries occur due to forces and accelerations. Modern impact biomechanics has been called “the science of injury control.” It is research into how to prevent injury through control of our environment. While this can include looking at sports injuries or insults due to slip, trips and falls, a large body of research has also been focused on automotive accidents.
Modern study of impact injury began in the 1920s. Hugh DeHaven, a combat pilot in World War I, survived free falling from a great height. This made him want to understand how people survive falls. More controlled laboratory research began in 1939 at Wayne State University in Detroit. What started as a collaboration between a neurosurgeon (Steve Gurdjian), and a professor of engineering mechanics (Herbert Lissner) led to a series of studies of head injuries and skull fractures using cadaveric skulls.
The 1930s also brought along collaboration between car manufacturers and medical experts, as a plastic surgeon (Claire Straith) described cranial and facial injuries in impacts with dashboards and windscreens during car crashes. He was “the first to recognize that it was automobiles that injured people. An accident was just the event, but it was the collision between the passengers and the inside of the car that caused the injuries.” This led to research into countermeasures like seat belts and padded dashboards. In 1934 General Motors performed the first barrier crash test which led to a more standardised testing of the forces in vehicular impacts.
Using data from injuries sustained during World War II, in the 1940s a neurosurgeon (Sir Hugh Cairns) and a physicist (Hylas Holbourn) at Oxford University gained insights into diffuse brain injury and concussion which led to biomechanical theories of brain injury that continue to be influential today. Researchers carried out experiments which established importance of head acceleration for onset of concussion. The use of helmets reduced mortality due to head injury in World War II motorcyclists. Holbourn hypothesized that the predominant cause of brain injury was not a result of linear acceleration, but rather due to rotation of the head. He measured shear strains during head rotation and postulated this as a major cause of brain injury.
In the late 1940s in the US, Colonel John Paul Stapp started running experiments which investigated the effects of deceleration on the human body. His experiments used early crash test dummies, volunteers and most frequently himself. This earned him the title of “Fastest Man on Earth.” Much of what we know about human tolerance, motion under deceleration, and safety harnesses comes from these early experiments. You can watch a fun public service announcement from the 1950s about his research here.
A key part in standardising impact testing in vehicles came in the early 1950s when Samuel Alderson started developing anthropomorphic test devices (more commonly known as crash test dummies) for testing jet ejection seats. In 1968, he produced the first dummy specifically for automotive testing, called the V.I.P. It had the dimensions of an average adult man, a steel rib cage, articulated joints and cavities which held instrumentation for data collection.
In the early 1970s, General Motors built a new dummy, Hybrid I by combining parts from Mr Alderson’s dummy with those of a rival, Sierra Engineering. Modern day crash tests and standards are still conducted using a newer generation of this dummy.
The 1960s and the availability of digital computing for research opened up possibilities of complex simulation which were not possible with simple calculations or even physical testing alone. As early as 1966, the Society of Automotive Engineers published papers by Raymond McHenry validating computer simulations to sled tests, with parameters such as seat belt forces, dummy accelerations and kinematics. The first computer program SMAC (Simulation Model of Automobile Collisions) was developed by McHenry in the early 1970s. While modern crash simulation programs have much slicker graphic interfaces, many are still using and improving on these early validation algorithms.
TRL has been at the forefront of research into impact biomechanics and vehicle safety since its infancy. In the early 1950s, researchers at TRL used analyses of data from road accident investigations and hospital records to highlight incidence of head and chest injuries to car occupants. Similar research is ongoing at TRL today, correlating collision dynamics with injury information in order to aid understanding of how people are injured on our roads.
Our experts draw on this rich history of research and their own experience to investigate and reconstruct accidents as well as drawing conclusions on injury causation and mitigation. Look out for Part 2 of this article where we will talk more about developments from the 1970s onwards, through to the present day.