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Abstract
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Limits to the systematic study of human tolerance to acceleration, as to other harmful environments, are set by possible experimental procedures. Animal and cadaver experiments have been valuable but do not completely reproduce live human response, while volunteer human exposure must stop well short of irreversible damage.
Epidemiology based on natural events has helped to fill in the gaps -- as in de Haven's original analysis of survived falls and more recent collections described by Snyder (1). These cases represent extreme values, for only a few subjects are known to have survived, and such values will necessarily have wide confidence limits. By analogy with toxicology, a useful measure of tolerance to a class of acceleration would be the LD50, the dose at which the mortality is 50%.
Naturally occurring falls of known heights can provide such data, when survived as well as fatal falls have been recorded. It should be possible to fix a data point for each height on a dosage mortality curve with impact velocity or height corresponding to dosage. Impacts with water sometimes fulfill the requirements for suitable records of a series of falls. Such a series from the Golden Gate Bridge in San Francisco, included in other data of Snyder's (2), appears to yield 97% mortality for a drop of about 240 ft (73 m).
The records of falls from two other bridges, the Sydney Harbour Bridge and the Story Bridge in Brisbane, Queensland, provide additional sources of information as to mortality for a given drop. |