An experimental study sought to extend understanding of the nosing-to-nosing method for measuring dimensions of steps in a stairway. A human factors expert retained to assist an attorney in a case of injury or death from a stairway fall needs to decide the lateral location for taking the measurements. This experiment was undertaken to provide experts with a justifiable basis for choosing the location. Using a campus stairway and 16 student subjects, a randomized complete block experiment compared their lateral location while performing four tasks—ascending with or without the handrail, and descending with or without the handrail. Results showed task significantly affected lateral distance. Based on findings from this experiment, and some professional judgment, the authors provide recommended ranges for the lateral locations for measuring step dimensions—30 to 38.5 cm for ascending, and 19 to 28 cm for descending.
Jensen, Roger C. and Calf Looking, Lee, "STAIRWAY UNIFORMITY MEASUREMENT: WHAT LATERAL LOCATION SHOULD BE MEASURED" (2018). Safety Health & Industrial Hygiene. 31.