Jerry L. Purswell

Coefficient of Friction and Subjective Assessment of Slippery Work Surfaces

Research was conducted to determine how well subjects could distinguish between surfaces with different coefficient of friction (COF) values and to evaluate how well subjective ratings of slipperiness correlated with the actual COF values. Thirty-three ironworkers experienced in working and walking on steel surfaces and 23 university students inexperienced with these tasks participated in the study. Subjective slipperiness ratings for a variety of climbing and walking conditions were obtained from the subjects. It was found that subjects could identify differences in the slipperiness of four types of steel coatings tested in the study. There was a high correlation between the subjective ratings and the measured COF values. Subjects did not slip at a COF of 0.41 but did lose footing at a COF of 0.20.

The Influence of Forearm and Wrist Orientation on Static Grip Strength as a Design Criterion for Hand Tools

The amount of force required to use a hand tool and its relationship to the users capacity to exert this force is a critical design criterion of hand tools, often affecting the immediate safety of the tool user and the propensity of the tool to cause injury to the user with long-term use. Because the wrist is often placed in deviated positions, the available data on grip strength with an undeviated wrist configuration may not be applicable to the design of many hand tools. This study demonstrates the decreases in grip strength due to wrist deviations and forearm rotation. The position of maximal static grip strength is the neutral wrist with a supinated forearm. Decrements from the neutral position for wrist flexion, hyperextension, radial flexion and ulnar flexion are 30%, 22%, 18% and 15%, respectively. The pronated forearm allows only 87% of the strength of the supinated forearm, and the differences between the supinated and the midposition forearm are not significant.

Behavioral safety program: Creating a new corporate culture

Abstract The traditional approach to safety in the workplace has been based on Heinrichs analysis of insurance data which he interpreted to conclude that most accidents are caused by “unsafe acts”. To reduce the number of ‘unsafe acts”, safety training, employee selection and supervision were applied as remedial steps. However, after many years of applying this approach, as well as incorporating workplace inspection through the Occupational Safety and Health Act (OSHAct), no substantial improvements have occurred in workplace safety. Thus the classical approaches to workplace safety have plateaued. Several field experiments have found that a behavioral modification approach to safety is an effective means to move from the existing plateau. The essential ingredient in the improved approach is motivation. An experiment conducted in a large industrial setting demonstrated the effectiveness of a well-designed behavioral safety program. A follow-up study at the same facility after two years indicated that the program did not produce a lasting effect. However, a few recent studies with a focus on the outcome of behavior rather than on the behavior itself have shown a more lasting effect on the safety behavior of workers.

Human Factors in the Design of Effective Product Warnings

Warning messages for product use are important for the safety of the user and to fulfill the legal duty to warn on the part of the manufacturer. A number of issues related to the design of such warnings have been neglected by human factors specialists. The studies that have been done have been primarily for private companies or in conjunction with litigation after an accident has occurred. Thus, little is available in the open literature. This paper points out some related behavioral work which has been published and outlines the problems associated with designing effective product warnings. Suggestions are made for further research.

Psychophysically determined work-cycle parameters for repetitive hand gripping

Abstract Carpal tunnel syndrome (CTS) and other cumulative trauma disorders (CTDs) are responsible for a high cost to the industry. CTS and CTDs have been reported in many industries and their risk factors have been identified. CTD occupational risk factors include repetitive movement, forceful exertions, sustained or constrained postures, vibration, low temperature, and mechanical stress. Exertion period and work duration have also been reported as risk factors. The literature search revealed the need for analytical studies of work cycle parameters, and the need to determine empirically the safety exposure limits for these factors. Therefore this study was concerned with presenting an analysis and definition of the work cycle parameters and investigating the safety exposure limits of the work cycle parameters. The psychophysical adjustment method was used to investigate the effect of force, wrist angle, and exertion period on the maximum acceptable work cycle parameters. The work cycle parameters were defined using the engineering definitions and terminology. These parameters were the rest period, duty cycle, and rest-to-work ratio. Twelve female subjects participated in a 40-minute hand gripping task and were allowed to adjust their rest period in relation to a set exertion period. ANOVA showed that there were significant effects of force, wrist angle, exertion period, and their interaction on rest period, duty cycle, and rest-to-work ratio atα = 0.001. Regression analysis was used to develop prediction models for the rest period, duty cycle, and rest-to-work ratio as a function of anthropometric dimensions of the hand and wrist, age, force, wrist angle, exertion period, maximum voluntary contraction (MVC), maximum deviation angle (MDA), and the percentage of MVC. The results of the regression analysis indicated that anthropometric dimensions and age were not significant factors. Relevance to industry Several countries have initiated prevention programs to control the prevalence of CTDs and CTS in the workplace. An important ingredient of these programs is designing the workcycle to provide adequate recovery time. This paper presents an analysis and prediction equations of the workcycle parameters for different work and task conditions.

A Prediction Model for Consumer Behavior regarding Product Safety

The objective of this study was the development of a model to predict whether a consumer would use a product safely as a function of sixteen different individual variables. Subjects were presented with four consumer products to use in an experimental setting where the true purpose of the study was concealed. Discriminant analysis was used to develop a prediction model to classify subjects into categories of safe or unsafe behavior. Prediction accuracy ranged from 68–86 percent for different types of behavior. The research illustrated which variables are important in determining whether a product will be used safely and has implications for product design, warnings, instructions for use and training.

Warning Effectiveness: What Do We Need to Know:

The forensic area of practice for human factors engineers has brought into sharp focus the differences of opinion which exist regarding the effectiveness of warnings in bringing about safe behavior on the part of the user of a product. This paper addresses the major issues which the authors believe must be researched further to provide the definitive answers needed regarding the effectiveness of warnings in a variety of possible applications. A review of the literature will demonstrate that there are few studies of warning effectiveness per se, while there are many studies that address such issues as the need for warnings and presumed criteria for preparing effective warnings. It is suggested that further research is needed which addresses warning effectiveness in actual use situations, and in turn identifies the importance of such variables as stimulus energy level, information overload, risk perception, cost of compliance and the interaction of warnings, instructions and training.

Occupational accident research: Where have we been and where are we going?

Abstract Purswell, J.L. and Rumar, K., 1984. Occupational accident research: where have we been and where are we going? Journal of Occupational Accidents , 6: 219–228. The purpose of this paper is to try to evaluate and highlight the International Seminar on Occupational Accident Research held in Saltsjobaden, Sweden, in 1983. Initially a background is given in terms of the development of studies of occupational accidents in recent decades. Accident statistics — the basis for all accident studies — are discussed in relation to both a previous seminar, held in Sweden in 1975, and to the future. The question of whether occupational safety should try to find one model, a uniform methodology, is discussed but not resolved. The problems of validity, reliability and countermeasure evaluation deserve and have received considerable attention during the seminar. The most obvious change from the 1975 seminar was found to be the proportion of authors concentrating on finding effective countermeasures. In the near future we shall probably see further research to guide employers and lawmakers in their efforts to change the working environment, more standardization in terminology and statistics, a convergence concerning methods used, more interest in cost effectiveness studies and a further closing of the gap between research and application.

Strategies for Improving Visual Inspection Performance

This paper summarizes recent results obtained in inspection studies including several studies performed by the authors. Both static and dynamic visual inspection tasks are included. Based on these results, a proposed new integrated design procedure for inspection tasks that will approach the optimal design has been formulated. The review of recent research results includes the following primary variables: the speed of the item passing the inspector, the spacing of items, the percentage of defective items, the illumination level, the contrast between the item being inspected and the background, and the effectiveness of individual versus group inspection. The authors have used their research results in combination with the results in the literature to formulate new integrated procedures for designing inspection stations and job procedures. The authors have also analyzed the effects of inspector performance on the overall quality control plans already in use in industry. The economic effects of changes in inspector performance which result from redesign of the inspection task are then demonstrated as a part of the overall design procedure.

Auditory and Biomechanical Performance Requirements for Motorcycle Helmets

The purpose of this paper is to examine some of the problems presented by the wearing of a helmet in the sensing of information necessary for safe operation of a motorcycle. The paper is organized into three major areas. One area is concerned with a laboratory study of simulated motorcycle operation and the sensing of sirens and horns of motor vehicles at various distances for subjects wearing helmets and subjects who served as control that wore no helmets. The second study reported is a parallel to the laboratory study but it was conducted in an outdoor setting. The third area considered is a biomechanical analysis of the head and neck of a motorcyclist who sustains a blow to the head in an accident. The independent variables investigated in the two studies of auditory sensing were the type of helmet worn, the type of auditory information being presented to the subject, and the direction from which the auditory signal was presented to the subject. A motorcycle helmet with a full face shield and one without a full face shield were compared with a control level of a subject wearing no helmet. A warning siren and a motor vehicle horn were the two types of auditory signals presented to the subjects. The four directions of presentation of the auditory signal were front, rear, left and right. Both of these tests of the ability of the motorcyclist to detect the two auditory signals indicated that the helmet did significantly attenuate the signal and that the emergency vehicle siren or horn would have to be dangerously close to the cyclist before it could be heard as compared to the cyclist under the same conditions who was not wearing a helmet. The alleged problem of motorcycle helmets producing injuries to the cervical spine in certain types of impact situations was analyzed from a biomechanical standpoint. Some helmet designs were found to be capable of producing an injury to the neck for certain crash configurations between the helmet and a solid object. Suggestions are presented for modification of helmet design to significantly reduce the injury potential of the helmet for this type of injury, while at the same time protect the head from other types of injury.