ABSTRACT
Over thousands of years stair step geometry has been a subject of fascination, speculation, rule making, analysis, controversy and, more rarely, formal ergonomics study. This paper provides only a scant introduction to this history. While there are multiple reasons-such as comfort, energy expenditure, and safety-for choosing one geometry over another, the focus here is on fall-related injury prevention. Two potent patterns of systemic stair step geometry defects have been identified recently by US-based ergonomists. The first systemic defect has two components that, in combination, increase the steepness of a stairway. The first is a riser that is too great, and the second is an undersized going. “Going”, “run” and “tread depth” are interchangeable terms used in the UK, Canada and the USA, respectively, for the horizontal dimension of the tread measured nosing to nosing. (The “nosing” is the tread’s leading edge). An undersized going is generally a more potent defect than an oversized rise in contributing to missteps, departures from normal gait, which can lead to falls. The second systemic defect, non-uniformity of step dimensions at the top of stair flights and, to a lesser extent, at the base of stair flights, has only recently been recognized by ergonomists as warranting special attention. Non-uniformity has long been identified as a danger although, traditionally, there might have been more emphasis on rise uniformity than going uniformity. So stair
design and construction regulations have traditionally addressed the need for step dimensions to be uniform. However, there have been serious deficiencies in the ways rules are stated and then enforced, and these are now the subject of relatively intense examination.
