Improve Safety by Improving Human Performance

Human errors have been significant factors in almost every accident, equipment shutdown, or quality problem in industrial and manufacturing facilities. A study of accidents in refining and petrochemical plants (1) identified the following causes:

* equipment and design failures, 41%

*

* inadequate or improper procedures, 11%

* inadequate or improper inspection, 5%

* miscellaneous causes, 2%.

Some managers assume that virtually all human errors are the consequence of lazy, stupid or inattentive workers, so simply finding and punishing the guilty parties will deter others from making the same or similar mistakes.

However, this philosophy blinds managers to the situations that underlie most human errors, and usually does more harm than good. Instead of blaming human error on ill-trained or unmotivated workers, systems must be established to investigate and analyze near-incidents (commonly referred to as "near misses") so that root causes are determined and corrective actions are implemented to prevent recurrence.

To assist in this process, the American Institute of Chemical Engineers' (AIChE) Center for Chemical Process Safety (CCPS) has written a new book, "Human Factors Methods for Improving Performance." The text provides practical information that can be used to identify and correct error-likely situations in the workplace. This article describes five key elements that can he used by any facility to effectively reduce human error.

Performance-shaping factors

Humans are an essential element of any process system. To minimize human errors, managers must ensure that the worker interfaces, which include interactions with other workers as well as with the equipment and environment, are compatible with the capabilities, limitations and needs of the worker.

A performance-shaping factor (PSF) is anything that affects a worker's performance of a task within the system. PSFs can be divided into three general classes: internal PSFs that act within an individual, external PSFs that act on an individual, and psychological or physiological stressors (2).

Table 1 lists some internal PSFs, which are the individual skills, abilities, attitudes and other characteristics that a worker brings to any job. Some of these, such as training, can be improved by managers. Others, such as a short-term emotional upset triggered by a family crisis, are beyond any practical management control (however, a manager's style can influence workers' mental/emotional states, as can counseling programs). Note that the PSFs managers often focus on, such as motivation and work attitude, are generally the more difficult to address. Telling someone to improve his or her attitude usually has nothing more than a temporary (and sometimes opposite) effect it the underlying PSFs are not addressed.

Table 2 lists external PSFs that influence the environment in which tasks are performed. External PSFs are divided into two groups: situational characteristics, and task and equipment characteristics. Situational characteristics are general factors that may affect many different jobs in the plant. They typically describe what it is like to have a specific job at a facility, such as that of an outside operator. Task and equipment characteristics are pertinent to a specific job or to a specific task within a job. These characteristics describe what it is like to perform a specific task, such as charging a batch of material. Job and task instructions are a particularly important part of the task characteristics because they have a significant effect on human performance. By emphasizing the importance of preparing and maintaining clear, accurate task instructions, managers can significantly reduce the likelihood of human errors.

The interaction between internal and external PSFs creates stress within the individual performing the task. Mismatches between internal and external PSFs result in disruptive stressors - i.e., stress that degrades job performance.

If too little stress is present, a worker will not remain sufficiently alert or motivated to do a good job. For example, a control room worker who repetitively fills batch tickets may not be alert enough to notice that an ingredient was omitted.

On the other hand, too much stress will quickly overburden a worker and degrade job performance. In such situations, workers tend to focus on the largest or most noticeable signals and ignore some information entirely; omit or delay some responses; process information incorrectly and reject information that conflicts with their diagnosis or decision: or mentally and/or physically withdraw from the task at hand. Examples of disruptive psychological and physiological stressors are listed in Table 3.

Although stress usually has a negative connotation, some stress is actually necessary for humans to function at optimum performance, as illustrated in Figure 1. Facultative stress is anything that arouses us, alerts us, prods us to action, thrills us, or makes us eager. When a positive balance exists between internal and external PSFs, workers experience facultative stress and their job performance is at its best.

Managers must recognize that most PSFs (including many internal ones) are within their control. By designing work situations that are compatible with human needs, capabilities and limitations, carefully matching workers with job requirements, and rewarding positive behaviors, managers can create conditions that optimize worker performance and minimize human errors.

General approaches for reducing human error

When contemplating ways to improve human performance, managers must address two basic types of errors - those for which primary causal factors are individual human characteristics unrelated to the work situation, and those for which primary causal factors are related to the design of the work situation. Employing appropriate hiring and job assignment policies is an important means for managers to reduce the causes of the first type of error. But, on any particular day. a worker could be emotionally upset, fatigued, and so forth, and commit an error. However, human factors specialists estimate that only 15 to 20% of workplace errors are caused primarily by such internal human characteristics.

The vast majority of human errors - 80 to 85% -result primarily from the design of the work situation (i.e., the tasks, equipment and environment), which managers can directly control. A work situation in which the PSFs are not compatible with the capabilities, limitations or needs of an employee to perform a task correctly is called an error-likely situation. In a sense, in an error-likely situation, a person has unintentionally been "set up" to make a mistake. Error-likely situations can result from a variety of causes, such as:

* deficient procedures (e.g., incorrect/incomplete/nonexistent, poor format, lack of warnings, inappropriate language, conflicting requirements, inconsistent with user needs/requirements)

* poor communication between workers (e.g., no shift overlap, vague verbal instructions, incomplete instructions, inconsistent instructions)

* inadequately trained workers (e.g., poor mental model(s) for diagnosing process upsets, little or no practice)

* conflicting interests of workers (e.g., productivity vs. safety, workers vs. management, operations vs. maintenance, practice vs. policy)

* inadequately labeled equipment (e.g., parts, raw materials, motor numbers, locations, etc.)

* equipment poorly designed for human use (e.g., inaccessible or inconvenient, violates expectations [such as a valve that must be turned clockwise to open], excessive or inappropriate automation, user needs are not addressed [e.g., a small control knob that must be manipulated by a worker wearing gloves]).

By providing the resources necessary to identify and eliminate error-likely situations, managers can reduce the frequency of human errors. Instead of setting up workers for error, they are set up for success.

This strategy is called the work-situation approach. To maximize the benefits of such a strategy, managers should solicit workers' input into this strategy at every opportunity. The workers can best identity factors that hinder their performance, and they likely will enthusiastically support such a strategy if they are not penalized for telling the truth. In addition, human factors specialists can be employed to provide expert assistance in implementing any changes. The work-situation approach involves the following five elements:

1. Implement good human factors engineering of equipment, control systems and the work environment

Many human errors are caused by equipment and work environments that were not initially designed with an emphasis on how humans would interact with them (i.e., operability, maintainability and human factors engineering principles). Therefore, a new system-design plan should account for: all necessary operational and maintenance behaviors through proper labeling and visibility; accessibility for use, repair, removal and replacement; proper inspection and testing; and availability of spare parts and tools. Examples include handles that can be grasped and turned with reasonable force, labels that can be read from a reasonable distance, and critical and/or unique tools permanently located at the job site. Where possible, error-proofing principles should be used to eliminate the potential for error, such as unique hose fittings that can only be connected to the correct tank, or a computer that can be programmed to accept only data in the valid range.

Identification and elimination of error-likely situations early in the design phase is obviously more desirable than the frustrating and costly task of retrofitting. Because most designs are based on a similar system currently in service, evaluating the existing system to help determine future requirements is prudent. Reviewing old drawings, performing walkthroughs, and interviewing operators, maintainers and other experienced personnel are effective ways of determining the requirements and identifying error-likely situations for a new facility. Including these personnel in the design reviews, or including them as permanent members of the design team, is an excellent way of involving the users (and possible future owners) of the new process in the design phase and using their knowledge and experience to help identity potential error-likely situations. The availability of these resources during design reviews has other advantages as well, such as providing costeffective and practical ways of addressing the problem areas that are identified, offering an excellent opportunity for training on the new process, and developing a sense of ownership of the new process among workers.

Many resources, such as checklists that systematically walk the user through different human-factors considerations, are available to help maximize the benefits of design reviews (for example, Ref. 3, pp. 384-388 and Ref. 4. Appendix 1).

2. Provide clear, accurate procedures, instructions and other job aids

Many human errors can be prevented by ensuring that clear, accurate procedures and job aids are available and appropriately used by all workers. In addition to reducing workers' reliance on skill and memory to perform a task, procedures and job aids assist in decision-milking and help ensure that a given task is performed consistently. Written procedures provide step-by-step directions describing how and when to perform the various portions of the task. Job aids (e.g., flowcharts, decision tables and checklists) concisely organize information needed to diagnose problems and plan tasks, and assist workers in performing tasks that involve numerous steps.

A procedure or job aid's effectiveness at reducing errors is increased by incorporating the following key principles:

1. Select a procedure style or format that is usable and familiar, and that best communicates the information to the worker. A consistent style and format will assist workers in finding relevant information.

2. Ensure that the procedure is accurate and complete in order to maintain credibility and to facilitate continued use. If procedures contradict the way tasks are actually performed, workers will soon lose faith in the procedures and will not use them. Create and maintain accurate procedures by involving experienced workers in procedure development and establishing a proper frequency for updating procedures (e.g., after any relevant equipment modifications). To further ensure that procedures remain accurate, have them reviewed periodically by experienced workers.

3. Include the appropriate level of detail in each procedure. Too little detail will make the procedure useless to the inexperienced worker, too much detail may discourage the experienced worker from using it. The appropriate level of detail depends on the level of worker expertise and the criticality of the task. An easy check is to ask a "qualified" person who does not normally perform the task (e.g., someone who might temporarily perform the job if the regular worker were absent) to follow the procedure. Inclusion of warnings, cautions and other critical parameters is appropriate for all levels of worker expertise. Some procedure formats, such as an outline, allow experienced workers to identify the highlights, yet still provide the inexperienced worker with sufficient details to perform the task.

4. Use language that is understandable to the worker in order to reduce the potential for errors, especially in stressful situations (hurried to complete a task, etc.). Procedures can be made more understandable by (1) including only one action in each procedure step, (2) using clear and simple language, (3) using the active voice for the actions (e.g., "open the coolant valve," not "the coolant valve shall be opened"), and (4) using short sentences and positive phrases.

Procedures and job aids must be readily available to encourage their use. Ideally, the procedures should be located where they will be used. For example, the directions on how to use a sample station should be located on the front of the access door. Alternatively, a single set of procedures should be kept in a central location that is readily accessible to all workers. If procedures are stored electronically and only printed when needed, sufficient work stations and printers must be provided to give the workers convenient access. Workers should not be allowed to keep their own personal copies of procedures unless a system has been implemented to control and update all the copies.

3. Provide job-relevant training and practice

Training ensures that workers possess the basic skills necessary to effectively perform their functions. Proper training of workers is critical to reducing human errors. Several types of training have proven most effective in reducing human errors, including initial skill training, refresher training, and management systems training.

Classroom knowledge-based training provides the basic expertise, technical background and understanding of the procedures. Initial skills training is a bridge between the knowledge-based training and on-the-job performance. It is generally conducted in the classroom and supplemented with on-the-job experience, and should be viewed as the means for preparing workers for real experiences they will routinely encounter, as well as those they will infrequently encounter. If skill training does not include the critical infrequent events or situations, the likelihood of successfully handling them will depend solely on the problem-solving and decision-making skills of the worker (which may not be sufficient).

In addition to the initial training, refresher training on nonroutine or modified tasks will minirnize worker errors and reduce the potential for a worker's skills to deteriorate. A refresher training (or practice) program that regularly challenges the worker's knowledge and provides opportunities to practice skills is needed to assist workers in developing and maintaining a high skill level, and enhancing a new worker's skills beyond the initial training level. The sawtooth curve in Figure 2 indicates the potential benefits of refresher training on worker responses by illustrating the conversion of knowledge to skill through repeated training and practice.

To round out a training program, regular training is required to ensure that workers can readily identify and follow relevant management systems. To prevent a common-cause human error, many companies have policies for redundant checking of critical tasks by different personnel. For example, the equipment may be aligned by one worker, checked by another, and verified by the supervisor before the procedure is started. Examples of other management systems include management-of-change procedures, safe work practices, and pre-startup reviews.

4. Provide ways to promptly detect and correct human errors

Many human errors can he prevented by implementing certain administrative controls and systems. For example, a buddy system that require employees to work in pairs for certain activities can he effective in detecting a human error before an undesired consequence occurs.

Many activities provide the opportunity to proof-test the recently completed task. For instance, after a maintenance technician finishes working on an instrument, it can be bench-tested to verify that the work was completed satisfactorily. Workers should identify opportunities to proof-test their work in order to detect mistakes before batches are started and equipment is returned to service. Whenever possible, these proof tests should be incorporated into written procedures to help ensure that they are effectively performed and to provide training for new employees.

Workers can also detect and correct human error through self-checking techniques, whereby a person consciously and deliberately reviews the intended action and expected response before performing a task.

One self-checking technique used in the medical field is the "five-rights" of administering medications:

* Right patient

* Right medication

* Right dose

* Right route (oral, intravenous, dermal, etc.)

* Right time.

A more general self-checking technique, developed by the Institute for Nuclear Power Operations, is the four-step STAR (Stop, Think, Act, Review) technique:

* Stop - organize your thoughts and eliminate distractions.

* Think - locate the correct instruments, items, procedures, and people; sense everything around you by listening, looking, smelling, and touching (as appropriate).

* Act - confirm the correct time, amount, equipment, parts, chemicals, etc.; perform the task carefully and safely.

* Review - observe what occurs when you have completed the task: verify that you have performed the task correctly; take appropriate follow-up actions.

Clearly, a person could not (and should not) employ this technique for every task. Thus, knowing when to use this technique is important. Table 4 provides a starting point from which cues can be developed for a specific work environment.

5. Provide avenues for workers to meet their social and psychological needs

People seek to satisfy what psychologist A. H. Maslow calls the "five basic needs" (5): existence needs (food, drink, air); security needs (shelter, secure sources of the existence needs, freedom from fear); social needs (affection, belonging to a group); esteem needs (being valued by others, recognition); and self-actualization needs (self-fulfillment, achievement).

Maslow recognized that "system factors," such as equipment design, procedures, training and organizational culture, are keys to motivating workers. Worker motivation will likely be high if (1) management applies accepted human-factors principles to job tasks, (2) employees receive training to develop the skills needed to handle contingencies, and (3) workers are actively involved in shaping their jobs. In addition, many first-line managers are given the opportunity daily to shape the work environment and to motivate workers to improve their level of performance. A motivated workforce with a positive attitude is less likely to commit errors such as those associated with internal human characteristics.

A team leader or supervisor who introduces various motivational factors into the work situation will help reduce the likelihood of human errors. These factors include:

* recognition - extending praise in the presence of his peers to the technician who reported a quality concern that led to the discovery of problems in the sampling process

* access to information - allowing and training a maintainer to obtain information on the computer system normally used only by the operators

* utilization of abilities - allowing a computer-savvy operator to provide input into the selection of the hardware and software for the new computerized management system

* challenging assignments - giving the central stores staff the opportunity to assist in determining the optimum distribution of compressed-gas bottles to the laboratories

* extended responsibilities - allowing a clerk, who has shown both the interest and the ability, to move into a position normally filled by people with college degrees

* freedom to act - empowering a technician to requisition new personal safety equipment without prior approval from the immediate supervisor

* involvement in planning and problem solving - inviting workers to participate in incident investigations, budget forecasting or goal setting

However, beware of outcomes opposite of those intended. For example, lavishly praising "heroic" work in response to a compressor failure may devalue the "boring" preventive tasks that could have prevented the crisis. Praising individual initiative may encourage workers to bypass formal management-of-change systems. The supervisor's challenge is to positively reinforce all desired worker behaviors, not just a few special cases.

Concluding thoughts

Most system performance problems and incidents are the result of human error. However, many of these errors are the result of error-likely situations created in the way systems are designed, operated or maintained, procedures are written, and training is conducted. Today's management is challenged by a paradigm shift from blaming mistakes on carelessness and incompetence to implementing methods to identify the root cause of a person's mistake. Allocating time and resources to understanding human factors, and identifying and eliminating error-likely situations through methods such as the work-situation approach, will significantly help to improve overall system performance and process safety.