How reasonable is reasonable use? The search for safer stepladders

Abstract

Stepladder accidents continue to be a major cause of injury at home and at work. Despite this, few changes have been seen in their design or their labelling. Many of the accidents occurring appear to be whilst the stepladder is being utilised in a manner which the user considers reasonable, but the manufacturer considers abuse. This work, sponsored by the Health and Safety Executive, investigates whether this mismatch can be eliminated in order to improve safety. The research combines user profiling with dynamic trials to establish what behaviour stepladders need to sustain. Through innovative measuring techniques, the demands on the stepladder system are quantified and the margin of safety calculated. Extensive dynamic trials generated data for over 4000 user, stepladder and task combinations. Individuals were given demanding tasks, but permitted to undertake them in a manner they considered reasonable and the resulting data can be considered as representative of the demands they would place on stepladders in everyday use. From this data, the stepladder and user system has been modelled, allowing manipulation of the stepladder parameters such that a virtual stepladder can be created which provides sufficient stability to tolerate all reasonably foreseeable use. In addition this model is used to generate predictive software which can determine the level of safety provided by real, or theoretical, stepladders. In conclusion, a specification for a simple test is given which could be routinely conducted to determine whether any given stepladder will offer the minimum level of stability considered necessary for safe use.

Analysis and testing of a hidden stepladder hazard – excessive twist flexibility

“…three support points are all that is required to support an object on a surface). Previous stepladder testing has shown that even when all four ladder feet are positioned properly on the ground, only three legs experience a significant groundreaction force at any particular instant and that these 'foot triplets' carrying the load periodically and abruptly change as the climber moves on the ladder (Clift et al 2002). Threeleg contact, where one rear leg actually loses contact with the ground, can develop under a number of situations such as set-up on an uneven surface or when climbing, sliding, pivoting or 'walking' a flexible ladder along the ground as the user's work progresses.…”