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Human Factors

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Safety Subject Information:

A ONE STEP HAZARD ALMOST KILLS CASTRO

ONE NEARLY GOT CLINTON, TOO (Actually, two)

It was the step seen around the world.  Fidel Castro finished up one of his long-winded diatribes.  He started out to greet his adoring public.  As he stepped from the dais, he missed the step and hurtled to the ground.  After a long hospitalization and convalescence, he relinquished the Presidency of Cuba to his brother, Raoul.

A simple fall over an easily controlled and well recognized hazard changed world history!

What of the hazard?

One-step or single step hazards are not generally encompassed by the definition of stairway (two or more risers with appurtenant treads). However, the hazards are essentially the same. The hazard is magnified by the absence of visual cues of the existence of a level change. One-steps are often used only for aesthetics in places where they can be unexpected. Conversation pits are "the pits", and sunken living rooms should be "sunk."

Where there is difficulty in discriminating a step nose due to inadequate light, a likelihood of sensory impairment in surface users, or a confusing surface pattern or coloration, or other irregularity, good practice demands highlighting the steps with delineation stripes or similar treatment applied to the nose edge. To avoid giving users a false cue, the stripes must extend to the edge of the nose. If they stop short of the edges, users will tend to identify the edges of the stripes as level edges, lose their balance, and fall.

Surface users may be caught unaware by an unusual physical feature such as an unnecessary step in a walkway area. In such a location contrasting colors of floor surface, nose delineator stripes, and even a physical barrier such as a railing, may be required to provide a satisfactory degree of safety.

Accident investigations and analysis show that the overwhelming majority of falls occur in transition from flat to inclined modes of travel, from inclined to flat, and at level changes. Accident statistics also show that the first two and last two steps of stairways have the most frequent accidents. A single step tends to combine the zone of transition at both ends into one hazardous area.

The popular press also recognizes the hazards associated with single step hazards. One example appears in the April 1985 New Shelter Magazine: "It is never a good idea to use a single step between two levels of decking--the difference in levels is so slight it can be hazardous. Better to have a minimum of three, 6-inch risers for each level change." The NBS book Guidelines for Stair Safety as well as other authors have written on the science and dangers of single steps (Templer, English, Rosen).

Often a one-step will have a riser that is too low to comply with the building code stairway riser minimum height. Sometimes a linear shadow line will make the step disappear. Patterns in a floor covering can also disguise the true edge of the step.

Single steps are particularly dangerous for several reasons beyond those associated with stairways. The difference in level between the upper and lower landing may be insufficient to provide visual discrimination of the drop. Color changes at the step are frequently ignored by floor covering installers. The single step will not be treated as a stairway with the associated visual cues, railings, or warnings. Regular users or the custodians of the one-step may not consider it sufficiently dangerous to require a warning. Finally, a single step may be placed in a location where there is little or no structural necessity for it.

A single step is not permitted in exit ways by codes ( NFPA 101. CCR Title 24, IBC.)

I can help you win one step, single step and stairway cases.

Copyright 2000 - 2011, Jay W. Preston.  Distribution permission granted when this notice is printed in full.  For questions or comments: contact prestonoidaol.com.  The J-P, Plus Design and SAFETYBIZ. are registered service marks of Jay William Preston. Permission for use of specific Safety Subject Information is only granted when this notice is printed in full and Preston has been contacted by phone, fax, or email prior to use.