A Macro-ergonomic Approach to Managing Slips and Falls in the Workplace

Transcription

1 A Macro-ergonomic Approach to Managing Slips and Falls in the Workplace Wayne MAYNARD and David CURRY Liberty Mutual Research Institute for Safety, Hopkinton, MA, USA and Packer Engineering, Inc., Naperville, IL, USA Abstract. Slips and falls are more than a trivial problem. Same level slips and falls represent nearly 11% of all workers compensation claims and over 13% of all claims costs. In most industry groups, slips and falls either represents the highest or second highest type of workers compensation claim (Leamon and Murphy, 1995). In addition, 11% of low back pain related claims and 12% of low back pain related claims costs are attributed to slips and falls (Murphy and Courtney, 2000). Yet, according to the Liberty Mutual Executive Survey of Workplace Safety released Spring of 2001, most executives perceive Falls on Same Level to be much less of a problem. Why the disconnect? The answer may be that managing slips and falls is traditionally a reactive process. Unsatisfactory injury trends, a serious incident and lawsuits trigger interventions. This paper will explore the human factors of slips and falls, traditional organizational culture associated with slip and fall prevention and offer a practical proactive systems analysis model of prevention that includes participation of all major stakeholders inside and outside the organization. Keywords. Macroergonomics, slips, falls, safety 1. Introduction Pro forma investigations of falls resulting in injuries often erroneously conclude that the fall was the result of a slippery walking surface. In reality, most common walking surfaces are inherently slip resistant and many factors lead to falls, of which the occasional slippery surface is only one. Goetsch (1993) identified four primary contributing factors to slips, trips, and falls: 1) a foreign object on the walking surface, 2) a design flaw in the walking surface, 3) a slippery surface, or 4) an individual's impaired physical or mental condition. In order to effectively prevent slips/trips/falls, it is necessary to have some understanding of how they occur. Four disciplines should be associated properly investigating slips, trips and falls. Tribometry involves the measurement of the slip-resistance of the walking surfaces. Ergonomics takes information about the capabilities and limitations of humans, and employs them in the design process to maximize both productivity and safety. Biomechanics involves the mechanics of muscular activity, in falls that of locomotion. Psychology comes into play examining the cognitive and perceptual issues involved in safely negotiating a walking surface while avoiding obstacles.

2 2. Gait and ambulation The gait cycle on a level surface begins with the heel strike (when the heel first touches the surface) of one leg, and includes the stance and swing phases of both legs. The stance phase is the period when the foot is in contact with the ground, while the swing phase is the period when the foot is off the ground. Three main subphases make up the stance phase: contact, midstance, and propulsive. The contact subphase begins with heel strike and continues as the front of the foot rotates downwards and becomes fully weight bearing. During this subphase, the foot both adapts to uneven surfaces and absorbs the shock of impact with the walking surface. During the midstance subphase, the foot begins to lift from the rear, preparing the foot for the propulsive subphase which begins as the heel lifts and continues through toe-off. The swing phase is the period during which the foot is not in contact with the ground; during this phase the foot recovers from toe off and changes its position to prepare for the next heel strike. The swing phase itself is broken down into two subphases: early and late swing. The former begins at the start of toe off, with both feet simultaneously in contact with the ground. The percentage of the cycle spent in the early swing phase decreases as walking speed increases, until the individual reaches running speed, at which time there may be periods when either only one foot is on the ground or both feet may be simultaneously off the ground. In the late swing subphase, the foot recovers from toe off and the locks into a rigid position in preparation for contact with the walking surface. The initial portion of the contact subphase is the point at which maximum friction is required in normal walking. As the heel strikes the ground at an angle, the forces imposed on the walking surface can be decomposed into two forces, with the first directed vertically downwards and the second directed forward in the direction of travel. Friction force between the shoe and the walking surface is required whenever the shoe is in contact with the ground, but reaches a peak level at the time of the initial heel strike (where it is needed to prevent the foot from continuing its forward motion). Two of the primary gait-related factors influencing the amount of friction required are the speed at which the individual is traveling and the angle at which the heel strikes. The higher the speed, or the more acute the angle at which the heel strikes the ground, the more friction is needed between the foot and the walking surface to overcome the forward directed force. Burnfield and Powers (2001) examined the friction requirements of a variety of subjects at several walking speeds. Results showed an average friction need of approximately 0.24 across ages, speeds, and genders. Slips occur when the coefficient of friction is lower than the ratio of the horizontal (F H ) and vertical (F V ) force components. A slip-resistance value of 0.50 under dry, clean conditions has long been recognized by the safety profession in the United States as being a slip-resistant surface. This value is advocated by Underwriters Laboratories, OSHA,

3 and ANSI (see UL 410, 29 CFR and ANSI A ) The ANSI standard cautions, however, that Floors, which do not meet the 0.5 guideline for dry conditions, should not be considered to be inherently dangerous. The Americans With Disabilities Act (ADA) cites the fact that individuals with walking impairments may require higher levels of walkway surface friction, and, in a non-mandatory appendix, recommends a slipresistance value of 0.60 on level walkways and 0.80 for ramped surfaces to accommodate such individuals. 3. Illumination and vision An often cited cause of stairway falls is lack of adequate illumination. Most building codes are relatively silent with regard to lighting requirements in these areas. Studies have shown that in normal stair negation only the top and bottom two or three stairs are usually visually mediated, making these the areas where lighting is most critical. This problem is most acute for older walkers due to physiological changes in the eye which can have a profound effect on object and edge detection. Additionally, for walkers wearing bifocals, the lower portion of the eyeglass lens is normally optimized to provide correction for close focusing. This may become a problem when objects at further distances (i.e., at floor level) are viewed through the lower portion of the eyeglass lens and the image becomes distorted. The result is an even greater loss of both depth perception and edge contrast sensitivity. Research (Lord et al, 2002) has shown that wearers of multifocal lenses are more than twice as likely to fall on stairs as wearers of single vision lenses. 4. Tripping Hazards A good safety program will normally encourage keeping the floor free of potential obstacles over which walkers may trip, but in many cases potential tripping hazards are a function of the walking surface itself rather than materials on it. Many building codes and other safety regulations and recommendations define any change in elevation of over ¼ as a potential tripping hazard. Abrupt changes in elevation of this height or greater are discouraged, and it is suggested that door sills and other similar obstacles be beveled. A trip occurs when the foot strikes a near ground obstacle that abruptly arrests the movement of the foot when the body s center of gravity is in motion. This causes the center of gravity to move out of the area of the body s support base, resulting in a fall. The most critical dimension of the foot kinematics involved in such a case is the toe clearance between the moving foot and the highest projection of the walking surface. The minimum clearance point is reached approximately halfway through the swing phase (Winter, 1992) where the foot has a 1.29 cm clearance height above the ground (about.58 ); variability for this height across subjects is about 0.45 cm (about.18 ). Assuming a normal distribution, this suggests that an obstacle height of ¼ may be a tripping hazard for 3.6% of the population, assuming that a walker encounters it at the lowest point in the swing phase and does not modify his/her gait to avoid it.

4 5. Macro-ergonomics and Prevention of Slips and Falls Ergonomics involves designing jobs to fit capability and limitations of people, while recognizing individual differences. In slips, trips and falls, often the most important individual difference is aging. According to Hendrick (2000), in the late 70 s managers were noticing the application of ergonomics/human factors at the micro-ergonomic level had significantly improved health, safety, productivity and usability of products. Still their work systems were not delivering the level of safety and productivity they intuitively knew should be possible. Correcting human factors problems at the operator workstation level did not correct problems at the overall work system level. Micro and macro elements must come together to effectively manage and prevent slips, trips and falls. Optimizing the working environment and thus reducing injury costs is critical to a safety process using a macro-ergonomic approach. Participation of key stakeholders inside and outside the organization is critical to the success of the program. A process which addresses prevention (pre-injury) and return-to-work (post-injury) is important. Key individuals who need to be involved include human resources, leadership personnel, safety and health professionals, engineering and maintenance, the health care provider, the rehab provider, the Worker s Compensation (WC) insurer and others. The worker is in the middle of this process, as well as communication between the worker and all other parties is essential for promoting safe behavior on the job and enabling return to work after an injury occurs (Robertson, et al., 2002). A managed slip and fall prevention process can similarly be depicted as a work system continuum with elements indicated in Figure 1. Management leadership Warning signs & instructions Floor slipperiness assessment Mats Slip-resistant footwear Slips, trips falls Education and training Incident and injury surveillance Hazard surveillance Housekeeping and maintenance Floor surface selection Floor surface treatments Figure 1. Slip and fall prevention continuum Macro-ergonomics offers a framework to conceptualize work system elements and is concerned with the design of the overall work system. It must involve the technological and personnel subsystems, as well as the external environment and the interrelationships between them (Hendrick & Kleiner, 2001). It is a top-down, sociotechnical systems

5 approach to the design of work systems and should involve employees at all organizational levels. Using systems analysis models and design processes, micro- and macro-ergonomic factors are identified throughout the work system design process (Robertson et al., 2002). Designing work systems that have congruent subsystems and alignment, and considers the sociotechnical characteristics of the organization can lead to substantial benefits such as increased productivity, health, and safety. Macro-ergonomics can be used to indicate why many slip and fall prevention processes are less effective then they otherwise could be. To conceptualize macro-ergonomic issues as related to slips and falls, a process can be described using the same three levels of the work system as noted above: organizational, group and individual. Within each of these levels, the socio-technical elements (technological and personnel subsystem) and the physical work environment factors can be related to potential outcomes that could measure the success of the falls prevention program. 5.1 Organizational: Senior management must take the lead and set an example for slip and fall prevention; this includes proactivity in prevention including holding managers and supervisors responsible and accountable for program implementation and the funding of interventions such as proper flooring and floor treatments, lighting improvements, slipresistant footwear, appropriate matting, etc. 5.2 Group: Everyone in the organization must work together to prevent slips, trips and falls. Stakeholder groups in a slip and fall prevention process include facilities management, operations management, risk management, safety, purchasing, occupational health, engineering, maintenance and housekeeping. Designing facilities to reduce risk by selecting the right flooring, matting systems, cleaning chemicals, footwear and more must be done right the first time. 5.3 Individual: Injury and hazard surveillance, or worksite analysis, is essential and must involve the worker. This is usually the weakest point of a slip and fall prevention process and no easy solution for dealing with the issue exist. Three safety and health surveillance approaches are recommended to assist managers and safety and health professionals in managing risks associated with slips and falls: 1) Employee reports: Prompt reporting of slips and/or falls with or without injury is important. Employees are often reluctant to do this due to embarrassment, and for non-injuries falls, there is rarely a system in place to accomplish this. The American Society for Testing and Materials (ASTM) addresses this issue in ASTM F1697 Standard Guide for Composing Walkway Surface Evaluation and Incident Report Forms for Slips, Stumbles, Trips, and Falls. The standard includes incident reporting guidelines, investigation approaches, information to collect and sample forms. 2) Review of existing records: Records such as Workers Compensation claims reports and OSHA logs can provide valuable information. Focus on this data, however, is a reactionary approach. Unfortunately, loss trends, serious injuries and expensive lawsuits (rather than proactive prevention) seem to drive most interventions.

6 3) Job surveys: These include facility audits, supervisor interviews with workers and surveys dealing with hazards. The challenge in dealing with slips and falls is that physical hazards are dynamic and variable from minute to minute. Employee involvement is thus critical. Clean as you go policies in the restaurant industry and maintaining sweep logs in the retail grocery industry are two examples of programs recognizing the dynamic nature of hazards, and can be an important part of a successful slip and fall program. 5.4 Technological subsystem: The technology subsystem includes proactive facility design to minimize hazards. This includes installing the right floor surface for the environment, selecting appropriate floor surface treatments, selecting front- and back-of-the-house matting, use of appropriate floor cleaning chemicals for likely contaminants, and selecting appropriate footwear. Aesthetics and cost often drive the selection of most of these interventions, but all are involved in a successful slip and fall prevention processes. 5.5 Socio-technical subsystem: Many managers in the organization do not understand their role in the slip and fall prevention process, nor the benefits of one intervention over another. Education and training on causes of slips and falls, their role in the process, and the importance of recognizing, evaluating and controlling hazards before they become expensive lawsuits/claims is critical to the success of the program. Training should also include technical training on types of floors, types of treatments or coatings, types of abrasive or grit material, chemistry of cleaning chemicals, design of slip-resistant footwear, design of matting systems and more. 5.6 Personal subsystem: Employees play an important role in the process. Their involvement can be promoted by offering flexibility of different footwear and styles. Employees should feel free to report hazards and incidences to their manager or supervisor without reprisal or penalties. Action should be taken to correct hazards as soon as possible. 6. Conclusion Slips, trips and falls are not well understood by many organizations. This in turn leads to prevention approaches that are reactive rather than proactive, only being triggered by undesirable loss trends or expensive injuries. The absence of proactive hazard and incident information such as the reporting of hazards, close call incidents, and incidents without injury further complicates the problem. Micro-approaches to prevention are usually not effective on their own, but when combined with macro-approaches can result in positive results over time. Preventing slips, trips and falls requires a combined effort among all members of the organization; communication across the entire work system is critical. Focusing on addressing problems at the work system level results in a safer and more productive work environment for everyone involved.