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NIOSH Safety and Health Topic:

Work Schedules: Shift Work and Long Work Hours

Filling the Workware Warehouse: What to Store with Regard to Long Work Hours

Extended Abstracts from Conference:
Long Working Hours, Safety, And Health: Toward A National Research Agenda
University of Maryland, Baltimore, Maryland
April 29 - 30, 2004
Using a multi-disciplinary approach, this conference explored the sociological, economic, and health dimensions of long work hours.

Donald I. Tepas
University of Connecticut
Storrs, CT


In the past fifty years there has been a significant expansion in the range and variety of work schedules employed. Thousands of different work schedules are now used around the world in a variety of environments. In a growing number of cases, instant real time decisions about working time arrangements are demanded in response to the immediate demand for work. This expansion in working time alternatives and change has been associated with a concomitant increase in research on the occupational safety and health impact of work schedules. Much of this research has focused on evaluating the impact of night work and seven-day-a-week operations on workers and their families. Currently there is a growing interest by managers in the use of long workdays and workweeks to increase productivity. Unfortunately, relatively little research has focused on providing those interested in long work hour use with the valid and sensitive knowledge information tools they need to avoid health and safety problems.


A knowledge information model has been proposed to provide prompt technological support (Tepas, 2003). This model introduces the term workware to identify the array of tools and knowledge available to describe, change and/or evaluate work schedules. Figure 1 provides a general and preliminary view of this knowledge information workware system.

Figure 1. The Workware Knowledge Information Model

A key part of such a system is the workware warehouse, an electronic internet gateway. This information warehouse would provide interested individuals and organizations (the "users") with immediate access to a variety of usable and valid decision support systems aimed at promoting the prompt and appropriate use of work schedule knowledge. The task of filling and maintaining the workware warehouse is the duty of a working time professional (who one might label a "workware engineer"). As such, the working time specialist is primarily concerned with designing, feeding, and maintaining an internet-centric workware knowledge information system.


Figure 2. Workware Warehouse Decision Support Systems

A major aim of this workware information system is to make accurate and current information and tools about working time promptly available to users. The users of the warehouse information are the organizations, managers, and workers responsible for daily (weekly, monthly, annually) work scheduling efforts. Figure 2 provides a sampling of the workware decision support information systems which might be included in the warehouse system. It is reasonable to assumed that the users of the warehouse system will be intelligent people, but one can not assume that they will be knowledgeable with regard to all facets (technical terms, practices, findings and pitfalls) of work schedule use. Thus, it is very important that the terms and information entered into the warehouse be operationally defined, current, comprehensive, and accurate. They should accurately reflect generally accepted expert judgement.

Initial Task: Selecting the Right Warehouse Terms

The use of long work hours is not a new practice. From a long-term historical perspective, reduction of work hour length is a relatively new thing. In the United States , outside of the commercial transportation industries, there are still few (if any) legal limits on the length of the work day. It is as if we had an honor system in place, whereby we depend upon common law injury suits and/or labor contracts to protect individuals and the public from unsafe/unhealthy long work hours. When hour limits exist, they appear to be most often based on political and/or economic considerations, not recommendations that flow from health and safety research. One result of this is that the potential hazards of long work hours are often described using popular, but poorly defined, constructs. Figure 3 provides some examples of these terms.


Figure 3. Some Popular Constructs Associated with Long Work Hours.

Unfortunately, poorly defined terms such as these may be beneficial for communication and media public discussion, but they are too global and multidimensional for effective workware warehouse use (Tepas and Price, 2001). There is nothing magical about an electronic Internet system. A knowledge information system based on ambiguity and global terms is not likely to yield precise recommendations and good decisions. For warehouse use, one needs terms that can be given clear operational definitions. Few of the needed operational definitions exist. Figure 4 shows some work schedule variables that probably can be defined in an operational manner, and therefore are more suited to workware warehouse use. Although attempts have been made to provide operational definitions for some of the terms in Figure 4 (see, for example, Tepas, Paley and Popkin, 1997), these terms remain fuzzy and in need of better operational definitions (Gärtner, et al, 2003). For example, what are "long work hours" (terminology used in the present conferences title)? So, for example, a primary next task we need to do is agree on an operational definition of "long working hours"!


Figure 4. Some Operationally Definable Work Schedule Terms

Second Task; Recognizing What We Already Know

Currently, workware designed specifically for long work hours’ problems is modest and limited. However, decades of working time research has resulted in some basic and general research-based conceptions, which should guide and direct experts filing the workware warehouse. Figure 5 lists some of these key general conceptions. In many cases the conceptions are counterintuitive, and a brief description follows. From the beginning, workware knowledge information systems should be designed to assure that the naïve user does not overlook these concepts.


Figure 5. Basic Conceptions

TIME-ON-TASK. This refers to how long a person has been doing something. Intuition suggests a linear relationship, wherein the longer you have been doing something the more likely it is that a worker will have an accident or be sick. Quite contrary to this, research has clearly demonstrated that for some tasks the relationship is not linear.

TIME-OF-DAY. Most transportation hours-of-service regulations assume that all hours of the day are equal with regard to their impact on the worker. In the service and manufacturing sectors, it is often assumed that worker ability is the same at all hours of the day. Research has shown that circadian variations in performance do occur, and that the peak time of day for performance many vary by task type.

TASKS PERFORMED. This refers to what a person is doing, as compared with how long the person has been doing the task(s). Intuition again suggests a linear relationship, wherein the more difficult/frequent/heavy the task is the more likely it is that a worker will have an accident or be injured. This assumption ignores the fact that inactivity, monotony and boredom can have a negative impact on worker performance.

ENVIRONMENTAL CONDITONS. Industrial hygiene exposure recommendations have long recognized the significance of heat, cold and noise exposure levels. For example, when air conditioning is absent, working time preferences can vary by season of the year. Thus, in a Northern temperate climate, workers employed on hot work tasks may prefer to work the night shift during the Summer, and the day shift during the Winter. Many work schedules ignore seasonal environmental changes.

DEMOGRAPHIICS. Little is known about the way age, gender, and household status mediate the impact of long work hours on American workers. For decades, the ILO, many nations, and some American states have had prohibitions related to the work hours of women and children. In present times, political and economic factors appear to have minimized these prohibitions. It does not seem that these, and other demographics, should be ignored by workware systems. Without a doubt, long work hours interact with demographics.

WORK/NON-WORK SEPARATION. Some transportation hours-of-service regulations do limit non-work behavior, or behavior following long work hours. In any case, there is a growing body of data that blurs the traditional boundary separating work hour behavior from non-work hour behavior. For most jobs, one can no longer afford to totally ignore the interaction of work and non-work health and safety behavior.

ACUTE VERSES CHRONIC IMPACT.In setting exposure limits for physical agents, industrial hygienists have often set different limits for short-term and long-term exposure to the same agent. Working time research clearly suggests that a similar approach is warranted when one considers employing long work hours. For example, one long workday may have an acute impact (or no impact), but many consecutive long workdays may produce a chronic impact which may have quite different health and safety consequences.

EXPOSURE RATE NOT INJURY AND ILLNESS COUNTS. All too often, simple counts of injury or illness numbers have been used as estimates of risk. Failure to consider risk exposure rate information can be quite misleading. For example, clustering of injury counts during the first few hours of work could lead one to conclude that long work days are safer than short work days. Government data bases maybe quite large, but very often they contribute very little to our understanding of the origins of occupational safety and health problems.

ORGANIZATIONAL SAFETY CULTURE. Management support of occupational health and safety training appears to be a crucial and critical component in many successful safety programs. It follows that work health and safety with long work hours might be improved, within limits, by a positive organizational safety culture. However, it is also true that a strong positive organizational safety culture should not be viewed as a substitute for using a bad work schedule.

NATION DIFFERENCES. Just as organizational culture can influence the impact of long work hours, nations may differ in the manner in which they support long work hours, night work, and irregular work schedules. In the contemporary global workplace, there is little reason to assume (as it often is) that the relative impact of long workdays will be the same in all nations. Existing nation differences in occupational task assignments, workforce demographics, public policy practices, and schedules history, all make it difficult to simply transfer working time technology from one nation to another.

Discussion and Summary

Just-in-time, flexible, on-demand, compressed, rapid-response, automation, on-line, and real-time are all terms that provide one with a feel for some general characteristics that many contemporary workplaces share. With these terms comes a demand for near-instantaneous changes in work schedules. All too often these changes include longer work hours, irregular work times, night shift work, and/or seven-day operations. Common sense tells us that some of these working time changes are not appropriate, since they may jeopardize worker health and safety. For sure, common sense decisions are not always right. Worse yet, changes in working time arrangements may be made without any consideration of health and safety issues. There are thousands of working time alternatives already in use, and the occupational safety and health of these alternatives need evaluation.

An internet-centric Workware Knowledge Information System is proposed as a solution to this real and practical problem. The users of this system would be the managers responsible for working time arrangements and/or the employed workers. Within this model, the work scheduling professional (termed the workware engineer) designs fills and maintains the Workware Knowledge Information System for users, but s/he does not apply it. A key requirement of such a system is the use of operationally defined terms. These are terms that improve the reliability of communication and promote valid technology transfer. Thus, filing the workware warehouse becomes a critical task wherein the workware engineer attempts to avoid the nomenclature errors of the past, and at the same time, builds on the general constructs and methods already established within the working time literature.

Clearly, there is a significant need for additional research on the health and safety aspects of long work hours. Some established basic and critical conceptions from the existing working time research literature are presented in this paper. These generalizations flow from families of existing empirical studies. They are not the product of isolated single studies or observations. At present, there are no instant solutions to the "long working hours’ problem". Excellent methodology and redundancy are needed! It should be recognized that individual studies of long working time impact often show false negative effects. The working time literature has shown us that the study of "survivor" groups, masking by unnoticed variables, and/or known but uncontrolled moderator variables, are all potential sources of error that a quality workware knowledge information system should be designed to detect and avoid.


Gärtner, J. Åkerstedt, T, Folkard, S., Nachreiner, F. & Popkin, S. (2003). Actually, is this the night shift? - Are shiftwork design-recommendations becoming meaningless due to fuzzy terms? Shiftwork International Newsletter, 20, 2, 73.

Tepas, D. I. (2003). Workware decision support systems: a comprehensive methodological approach to work- scheduling problems. Theoretical Issues in Ergonomics Science, 4, 319-326.

Tepas, D. I. & Price, J. M. (2001) What is stress and what is fatigue? In P.A. Hancock & P. A. Desmond (Eds.), Stress, Workload and Fatigue. Pp 607-622. Maahawah, NJ: Lawrence Earlbaum . .

Tepas, D. I., Paley, M. J. & Popkin, S. M. (1997). Work schedules and sustained performance. In G. Salvende (Ed.). Handbook of Human Factors and Ergonomic, 2nd Edition. Pp 1021-1058. New York: Wiley.


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Extended Abstracts from Conference Presentations:

Filling the Workware Warehouse: What to Store with Regard to Long Work Hours

Industry Trends, Costs and Management of Long Working Hours

Modelling the Impact of the Components of Long Work Hours on Injuries and "Accidents"

Organized Labor’s Response to Long Work Hours

Overtime, Occupational Stress, and Related Health Outcomes: A Labor Perspective

Work Hours as a Predictor of Stress Outcomes

Working in a 24/7 Economy: Challenges for American Families

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