Brady Holt, CC BY 3.0 , via Wikimedia Commons

Rusty Haight, the human dummy

A short while ago I had the opportunity to talk about Murphy's Law and crash testing, which allowed me to introduce Murphy and Col John Stapp who, albeit indirectly, have given so much to the development of automotive safety. Reflecting on the key figures in the industry, I said to myself that I could not fail to mention Rusty Haight: thanks to his invaluable 'sacrifice' our biomechanical damage indices are now more accurate.

Brady Holt, CC BY 3.0, via Wikimedia Commons

Brady Holt, CC BY 3.0, via Wikimedia Commons

So what is his contribution? Who is Rusty Haight?

There is no doubt that Rusty Haight is a forerunner in vehicle occupant safety testing. Director of the Collision Safety Institute (San Diego CA) he is called Human crash test dummy (literally 'the human crash test dummy'!) as the man who has performed the most crash tests himself . In fact, Haight has crashed into a wall in countless cars about a thousand times! It seems impossible, but he has never been seriously injured and still volunteers for experiments from time to time.

Many of the results of his studies have improved accident reconstruction techniques and helped car manufacturers to make safer cars. The results of his studies on the response of the human body to violent stresses and on road accident statistics have made it possible to raise the level of passive safety of means of transport, with the introduction of new design criteria, devices and regulations.

As discussed in the previous article the assessment of the safety of a vehicle in the event of a crash follows a biomechanical approach, in a nutshell we put dummies with various types of instruments and sensors on a car and by recording the data from the various sensors during a crash test it is possible to estimate the ability of the vehicle to protect its occupants.

Brady Holt, CC BY 3.0, via Wikimedia Commons

Brady Holt, CC BY 3.0, via Wikimedia Commons

At least two questions arise here:

What kind of quantities do we need to measure?

What is a man's threshold of tolerance?

Biomechanics comes to our aid: by applying its principles we can understand how physiological systems work under the action of an accident, but in the end it is experimentation that makes a strong contribution to identifying thresholds of tolerability.

Tests on animals or instrumented cadavers have made it possible to identify methods (what are called biomechanical damage indices) and thresholds. This is where the work of people like Haight makes an outstanding contribution! Animal and human cadaver tests will never allow such an accurate estimate: animals have different tissues from us, with different reactions to impact and external stimuli; non-living bodies are affected by the absence of muscular feedback during impact and (although it sounds bad to say it) by the state of decomposition.

As everyone knows, crash tests are currently not carried out on volunteers, animals or even cadavers, but on dummies, anthropometric dummies that attempt to reproduce the human body and allow the measurement of the quantities needed to assess injuries. The first Dummy, Sierra Sam, was created in 1949 and has undergone considerable evolution over the years to increase its bio-fidelity. There are now several families, each dedicated to different types of crash, and in each family there are different versions to cover the wide range of the population (age, size, sex, etc.).

National Museum of American History Smithsonian Institute, CC BY-NC-ND 2.0, via flickr

National Museum of American History Smithsonian Institute, CC BY-NC-ND 2.0, via flickr

The most popular of these is the Hybrid III family, which consists of: two male manikins of medium (50th percentile) and plus size (95th percentile), one female manikin of medium size and one male manikin of 6 years old. The Hybrid III family is used in most frontal impact tests. Obviously there are many families such as the SID (Side Impact Dummy) specific for side impacts, the THOR (the most sophisticated evolution of the Hybrid) and the new CRABI (small child representative dummies).

These dummies are extremely expensive, costing more than €100 000 to buy, and they have to be constantly checked, calibrated and repaired, because, of course, they too can be damaged during a crash test. Their cost may seem high, but without them, vehicle safety would not have today's standards of protection.

Companies that routinely use crash-testing to improve the safety of their products and to meet regulatory standards spend considerable resources on crash-testing and increasingly design solutions that reduce the time and cost of this important part of the budget.

Research and innovation in the field of Virtual Simulation over the last few decades is moving in this direction. A virtual phase that precedes crash tests and that uses numerical models of dummies makes it possible to better adapt the product to the type of impact to be tested and therefore to arrive at the homologation test only when the real conditions for passing it have been established.