SlipS and FallS

Injuries associated with slips and falls continue to be a significant burden to society, both in terms of human suffering and economic losses. Fall accidents are the second leading cause of accidental death in the United States (after motor vehicle accidents), resulting in more than 25,000 fatalities in 2009 and accounting for nearly 9 million visits to the emergency department (National Safety Council, 2011). Fall accidents also are prevalent in the occupational arena, where they are responsible for a significant proportion of worker absenteeism and disability leading to 1 or more days away from work. According to the U.S. Bureau of Labor Statistics, disabling work injures in the entire nation totaled approximately 5.32 million, and more than 14% of injuries involved slips and falls (Yeoh, Lockhart, & Wu, 2013; for additional information, see http://www.bls.gov/iif/oshcdnew.htm). In European countries, slip and fall accidents also contribute significantly to serious injuries, causing hospitalization and days away from work (Sicre et al., 2008). In this chapter, I elaborate several approaches used by ergonomics researchers to decouple the mechanisms associated with slips and falls, and I provide comprehensive guidelines for designing a safe living environment in which the risk of slips and falls is minimized. Ergonomics researchers have applied several different methodologies stemming from tribology (surface dissipative forces and hydrodynamics of two surfaces), psychophysics, and classical biomechanics to better understand the interacting mechanisms associated with slips and falls so as to design a safe living environment. I begin by discussing the tribological aspects of fall accidents, including the characteristics of surface dissipative forces, the characteristics of hydrodynamic properties, and the various devices to measure the coefficient of friction (COF) of floor surfaces. I also discuss guidelines regarding safe COF levels. Next, I discuss psychophysical characteristics, as the perception of the surrounding environments (e.g., slippery floor surfaces) also is important in fall safety. Psychophysical methods have been employed to investigate human judgments of slippery floor surfaces in an effort to provide input to comprehensive viscoelastic and hydrodynamic models of shoe–floor interactions. Researchers using the psychophysical methodology have asked research participants to subjectively assess the slipperiness of floors to obtain further insight into the parameters of vision and tactile sensation, which, in turn, is used to assess the discrepancy between a model (our perception of the floor surface) and reality (what we can currently measure). Furthermore, in analyzing the principles of body stability and the mechanism of slips and falls, it is necessary to understand the dynamic principles of human locomotion. In this section, I present the biomechanics of human gait to elaborate on the “human” aspects of slip and fall accidents. This information may provide a better understanding of the relationship among the various factors involved in fall accidents and may also assist in formulating cogent requirements for optimal human systems integration.