APS News

October 2011 (Volume 20, Number 9)

This Month in Physics History

October 21, 1914: Birth of Samuel W. Alderson, inventor of the crash test dummy

crash test dummy
Crash test dummy

The dubious distinction of being America’s first automotive casualty belongs to Henry Bliss, who stepped off a New York City trolley in 1899 and was struck and killed by an automobile. More than 20 million people have been killed in car accidents since then, and that number might well have been higher were it not for the ingenuity of a physicist named Samuel Alderson, inventor of the crash test dummy.

Alderson was born in Cleveland, Ohio, on October 21, 1914 and grew up in California. His father, a Romanian-born immigrant, owned a custom sheet-metal and sign shop. Alderson finished high school at 15 and periodically attended several colleges, including Reed College, California Institute of Technology, and the University of California Berkeley. His education was interrupted by stints of working in the family sheet-metal business. He pursued a PhD in physics at UC-Berkeley under J. Robert Oppenheimer and E.O. Lawrence, but never finished his dissertation.

Instead, he developed tiny electric motors for missile guidance systems during World War II, then went to work for IBM, where his research included designing a motor-powered prosthetic arm. Based on this work, he founded his own company in 1952, with a contract to design an anthropometric dummy to test the safety of the ejection seats used in aircraft. The automotive industry was also interested in such a dummy, as the number of traffic fatalities continued to rise.

The field of biomechanics was still brand-new, with no reliable data on the effect of sudden violent forces on the human body–and no good tools with which to measure such impacts. Researchers at Wayne State University in Detroit started experimenting using cadavers from its medical school– usually elderly white males. They placed accelerometers on the cadavers and strapped them into cars to study the impact on the bodies of head-on-collisions and rolling.

A handful of hardy souls volunteered to serve as living crash test dummies in the late 1940s by strapping themselves into rocket sleds to test the effects of rapid deceleration on the body, and by allowing themselves to be pummeled in the chest with heavy objects, and sprayed with shattered glass. These included Colonel John Stapp, for whom the annual gathering of car-crash testers is named, and Wayne State professor Lawrence Patrick. Patrick claimed the tests (while painful) were crucial to the development of the earliest mathematical models used in the field.

Later, live animals were used to collect data on survivability. Pigs were particularly well-suited to the task, since their internal structure was similar to that of humans, and they could be placed in a sitting position inside a vehicle.

Those tests, while controversial, provided the anatomical models needed to design the first crash test dummies–and also led to design changes in vehicles that have saved thousands of lives. A 1995 article in the Journal of Trauma by Albert King estimated that about 8500 lives each year are saved as a result of such research. In fact, for each cadaver used, nearly 300 people survived what would otherwise have been fatal crashes.

Yet those early models were imperfect, in part because no two cadavers were alike, making it difficult to collect reliable comparative data. An anthropometric test dummy (ATD) that could be mass-produced, tested, and re-tested, would address this fundamental flaw.

That was Alderson’s task when he founded his company. The first such dummy was dubbed “Sierra Sam,” introduced in 1949 to test aircraft ejection seats, aviation helmets, and pilot safety harnesses. In 1968 he produced the V.I.P., designed for automotive testing. It had a steel rib cage, articulated joints and a flexible neck, with cavities to hold instrumentation, and was designed to mimic the acceleration and weight distribution properties of an average male.

By the 1970s, General Motors scientists had entered the market, introducing the Hybrid I, combining aspects of Alderson’s original design with that of a competitor, Sierra Engineering. This was quickly followed by the Hybrid II and Hybrid III, with improved neck flexibility and head rotation to more closely simulate that of a human body.

The latter has been the industry standard since its introduction in 1977, expanding from just an average male dummy to include an entire “family.” It incorporates several sensors at key points on the “body,” to measure such things as the torque on the neck in response to a collision, or how much the seat belt compresses the chest.

The Hybrid series was designed specifically for frontal impacts, so there are now models of crash test dummies to measure the impact of other situations as well. These include the Side Impact Dummy (SID), to measure what happens to the ribs, spine and internal organs during side collisions: BioRID, to study the impact of rear collisions, particularly whiplash injuries; and CRABI, to study the effectiveness of seat belts and air bags on children.

One of the most advanced crash test dummies to date is WorldSID, capable of recording 258 separate measurements in a single crash test. But manufacturers continue to make improvements, such as RibEye, a prototype from Denton ATD, with LEDs on each of the dummy’s 12 ribs that can then be tracked by light-angle sensors, thereby measuring movement in all three dimensions.

Alderson went on to create humanoid figures dubbed medical phantoms, designed to measure radiation exposure, as well as synthetic wounds worn by soldiers during training exercises, capable of oozing fake blood. But it is his contribution to automotive safety, in the form of the crash test dummy, that has saved the most lives and become an icon of popular culture. Alderson died peacefully at home in Los Angeles on February 11, 2005, at the ripe old age of 90.


Further Reading
Guizzo, Erico. “Anatomy of a Crash-Test Dummy,” IEEE Spectrum, October 2007.
Roach, Mary. Stiff: The Curious lives of Human Cadavers. New York: W.W. Norton, 2003.

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October 2011 (Volume 20, Number 9)

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