Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Analogous Systems Human factors analysis gains value from its ability to generalize across domains. This is particularly true when empirical data are scarce and ad- vances in understanding may be achieved by sharing knowledge from simi- lar systems or paradigms. Yet the application of conclusions drawn in one domain to another must proceed cautiously and identify the ways in which the two domains are similar or different. It is with this caution in mind that we proceed with these comparisons, which may be based on a number of criteria, such as unique characteristics of the transition within each system (e.g., expectancy of an emergency occurring, level of risk, physical environ- ment) and factors of the system contributing to the emergency (e.g., faulty decision making, duty schedule, crew structure, communications, human factors design). The first part of the chapter enumerates the features of similarity in the team transition process in terms of five general categories: time, structure of the event, environment, risk, and organizational structure. These features are then described for each of the analogous systems of interest. Within the discussion of each system, relevant case studies are referenced illustrating how causes and contributing factors of an emergency or accident may be generalized, with caution, to the tank environment. FEATURES OF SIMILARITY Time The time element contains three areas of concern: the time constant of transition, expectancy, and the pretransition period. 28
ANALOGOUS SYSTEMS 29 The time constant of the transition refers to the abruptness with which a crisis transition unfolds and how it affects the manner in which the team is able to respond. For example, the transitions and responses to those transi- tions in a nuclear reactor typically unfold in a matter of seconds and min- utes; those at a fire scene or on the battlefield may involve minutes and possibly hours; the response to natural disasters may unfold over hours and days. Situations differ widely in the extent to which operators can expect that a transition will occur. Expectancy is a variable often driven by the fre- quency with which transitions have occurred in the past. For example, nuclear power operators rarely encounter serious failures. In spite of their recurrent simulator training to deal with emergencies, they operate under the assumption that the plant will continue to function normally. A similar situation probably exists for air crews of commercial airliners. In contrast, shock trauma and hospital emergency room crews maintain a fairly continuous level of preparation for medical emergencies and acci- dent victims, as they can be expected at any time. Tank crews fall some- where between these levels of expectancy. They are mobilized for an en- gagement, know that such an engagement will probably occur some time in the future, but they do not know precisely when. The difference in expect- ancy is potentially important, as it influences the speed with which people can respond to discrete events (Wickens, 1992), as well as to system fail- ures (Wickens and Kessel, 1981~. The pretransition period is related to, but distinct from, expectancy and describes the length of time that a given crew must remain on watch before an event may occur. For example, flight crews or nuclear power operators may be on duty for eight to ten hours before an event occurs (if at all), whereas hospital personnel may be on call for days, and battlefield necessi- ties may call on the tank crew to maintain themselves on station for as long as 72 to 96 hours. This time period clearly has the potential to influence the quantity and quality of rest in a way that can influence the post-transition performance. Structure of the Event The structure of the event refers to the extent to which its nature is predictable and whether the desired response can be effectively preprogrammed. Cognitively, this process may be described as updating a mental picture of the evolving situation. Because of the high complexity of nuclear power plants and the resulting complexity and multiplicity of their features when emergencies occur, reactor designers encounter major challenges in training operators for specific sequences of procedures or actions to be followed, given the variability of possible failures (Woods, 1988~. In contrast, the
30 WORKLOAD TRANSITION pilot of an emergency medical services (EMS) team will have a fairly proceduralized set of actions to be carried out in the process of getting the helicopter aloft and then to its destination, although the destination and the route flown to and from that destination may be wholly unpredictable. The degree of predictability of response in tank crew operations falls some- where in between. Environment Physical conditions of the environment play a potentially important role in the response to the transition. The conditions of the flight deck or nuclear power plant control room are relatively friendly temperature con- trolled, low to modest noise level, comfortable, and relatively free of vibra- tion. This is in marked contrast to the tank environment, in which four operators work within cramped, noisy, and vibrating conditions, often under excessive temperatures. Personal Risk Transition teams differ in terms of the extent to which they are exposed to risk of personal injury or death, both to themselves and to others. Risk may be realized at three different levels (i.e., before or after the transition period or not at all). For the tank crew, there is a feeling of risk the moment they enter the combat arena, whether in the pre- or post-transition period. The aircraft pilot or nuclear power plant operator experiences little risk until after a transition event occurs; the emergency room personnel or disas- ter relief organization may never feel the risk at all. Both risk and environ- mental factors influence the stress that is experienced in a way that can have serious effects on the abilities of crews to function effectively. Organizational Structure Organizational structure has three subcomponents: team structure (command authority), team integrity, and organizational autonomy. The dimension of team structure or command authority defines the ex- tent to which the unit does (e.g., the tank crew or flight deck) or does not (e.g., the nuclear power control room team) have a clearly defined chain of command or authority gradient. The authority gradient and its relation to the definition of job responsibilities can have a complex effect on perfor- mance efficiency (Foushee and Helmreich, 1988; Wickens et al., 1989; see also Chapter 10~. Team integrity refers to the extent to which crew members are main- tained as an integral crew over time or continue to belong to the same unit.
ANALOGOUS SYSTEMS 31 Tank crews generally possess such integrity. In contrast, U.S. airline crews are typically formed uniquely for each sequence of flights. It is generally assumed that team integrity is beneficial for team emergency response, al- though airlines believe that common training and proceduralized activities can compensate. This issue has been identified as important by other re- searchers as well (see, for example, Druckman and Bjork, 19919. Organizational autonomy defines the extent to which a unit functions alone or in close coordination with a higher organizational structure. Nuclear power plant operators respond to emergencies as a fairly self-contained unit, as do emergency room staffs. Firefighting units may have to coordi- nate with other units when the situation is serious. Tank crews nearly always need to do so. The need for extra-group communications and coor- dination typically places an added burden on the ability to cope with the transition. Summary The features of similarity described above are summarized in Figure 2.1, which identifies the set of features, and offers a line connecting the feature levels of the designated transition teams. Comparisons of two pro- totypical teams are shown: the tank (x) and the aircrew (o) (discussed below). COMMERCIAL AIRLINES Commercial airline crews typically consist of two or three members: the captain (or pilot), the first officer (or copilot), and possibly a second officer (or flight engineer), in addition to a support team of maintenance workers, air traffic controllers, cabin crew, and so forth. These crews may be on flights that take as little as half an hour or as long as 15 hours or more. The crews do not remain intact from flight to flight, so little crew planning can occur prior to the predeparture briefing. The reader is referred to Chapter 10 for a detailed discussion of the important aspects of leadership and coordination in the cockpit that affect team performance under stress caused by transitions in workload. A num- ber of airline accidents have been attributed to inadequate cockpit coordina- tion and management (National Transportation Safety Board, 1985a). In one case the National Transportation Safety Board reported that in many of these accidents there appeared to be little captain leadership and planning guidance for the flight (National Transportation Safety Board, 1985a) which led to the conclusion that all crew members should be required to be trained in crew coordination and decision-making skills that are essential to the . ~ . ~ sate operation of aircraft.
32 WORKLOAD TRANSITION Low Med High (short) (long) Time Constant Expectancy Sleep Loss Structure Environmental Stress Risk Command Structure Team Integrity Autonomy JO x ,'' Aircrews I Tanks - x . -a ~ FIGURE 2.1 Similarity of team transitions. As Figure 2.1 shows, air crews often have little advance warning that a crisis is about to occur, and when it does the crew must respond within seconds or, at most, a few minutes, depending on the event. However, as in the nuclear power environment, the probability that a transition or serious event will occur is quite low. When a transition does occur, though, one factor that is likely to affect the capability of the crew to respond appropri- ately and rapidly is the current flight and duty schedule of the crew mem- bers, which may be a period of 8 to 10 hours. As in a number of other systems, such as emergency medical services, the pilot will have a fairly proceduralized set of actions to be carried out in the process of taking off, flying, and landing. The environment is tempera- ture controlled but noisy, which makes intracockpit communications diffi- cult without the use of headsets and interphone (National Transportation Safety Board, 1980~. In addition, the cockpit is cramped, especially consid- ering the number of displays and controls that are present. If a transition occurs, the extent to which the crew is exposed to risk of personal injury is moderate. However, the crew will usually experience little risk until after the transition event occurs. In commercial airlines, the cockpit crew has a clearly defined chain of authority; however, U.S. crew members are never given the opportunity to adjust to how a particular pilot manages the crew because the crew compo- sition is reconstituted for each flight. Finally, the crew does not operate in
ANALOGOUS SYSTEMS 33 isolation but must coordinate and communicate with air traffic control, cabin crew, and maintenance. As identified in aircraft accident reports, several airline accidents have been attributed to a breakdown in air traffic control coordination (National Transportation Safety Board, 1985a, 1987~. At the same time, the availability of air traffic control can often serve as a valuable asset to flight crews in time of crisis. Upon examination of Figure 2.1, it appears that tank crews and airline crews do not have a great deal in common. Their time constants during transitions, expectancies of transitions occurring, environmental stress, team integrity or continuity, and group autonomy are very different. However, they are very much alike when one examines their duty schedules and com- mand structure. These latter two factors affect vigilance and monitoring behavior (Chapter 6) and communication flow (Chapter 10), which have been found to degrade team performance in both environments, as well as in numerous other systems. This seems to suggest that the communication flow and the type of information that is shared should be fairly well struc- tured and should be heard and understood by the receivers. Crew mem- bers need to receive pertinent information that is likely to affect team and system performance in a timely and easily interpretable format. These shared aspects between the two environments are highlighted in Chapter 10. A number of major transportation accidents raise serious concerns about the far-reaching effects of physiological conditioning (including fatigue and sleep patterns) and circadian rhythm factors in transportation system safety, in addition to the effects of the physical environment or workspace, train- ing, communication structure, and crew structure on system safety. Acci- dent investigations reveal that poor work-rest scheduling can jeopardize safety in most transportation modes (Graeber, 1988~. It appears that em- ployees and first-line supervisors in the transportation industry do not re- ceive training on the effects of work-rest schedules on safety and perfor- mance. Yet commercial airline crews frequently encounter irregular and often unpredictable work-rest patterns. It appears that, with minor excep- tions, neither management nor the labor segment of the transportation in- dustry properly considers the adverse effects of irregular and unpredictable cycles of work and rest on its vehicle-operating personnel. RAILROADS Railroad freight train crews until recent years were composed of 5- person crews; however, the current typical crew consists of 3- and, increas- ingly, 2-person crews. Amtrak and many other commuter trains are known to run with a crew of 1 in some areas. The typical 5-person crew is com- posed of an engineer, a conductor, 2 brakemen, and a fireman. The 3- person crew includes an engineer, a conductor, and a brakeman in the cab;
34 WORKLOAD TRANSITION the 2-person crew does not have a brakeman. The engineer is responsible for controlling the train. He has the written dispatch orders, receives infor- mation from the dispatcher, and is the sole decision maker. Both the engi- neer and conductor know the makeup of the train, but the trainmaster, the manager of the yard with respect to the movement of freight, determines the makeup, and the conductor keeps a manifest. This information will influ- ence the decisions made concerning stopping distances and train speed, especially when approaching curves and up/down grades. The brakeman couples and uncouples train cars, releases the hand brakes, and so forth. On all freight trains, there is a clear division of labor that has evolved since the 1800s. For example, eliminating the brakeman's position would have no effect on that of the engineer (T. Brown, personal communication, 19921. When a transition event unfolds in the railway industry, it does so in a matter of seconds. As in the commercial airline industry, the expectation that a transition will occur is quite low. The railway crew is "on watch" or "on call" at all times while on duty. This may affect the quantity and quality of the rest they get. At times, crew members have gotten only a few hours of sleep at a time, which leads to chronic sleep deprivation and has been cited as a contributing factor in at least one railway accident (National Transportation Safety Board, 1989~; however, a recent study (General Ac- counting Office, 1992) analyzed accident data of 30 engineers from each of 4 railroads and found no relationship between hours on duty and human- factors-related accidents. At least 80 percent of the engineers surveyed work, on average, 10 or fewer consecutive hours, but the time at which they were called to duty varied greatly and may have been a contributing factor. Railroad cab crews have highly irregular work-rest cycles; work and rest hours begin and end at any hour of the day or night. If a crew works up to 8 hours, the law requires that they have 8 hours off immediately after. Crew members are called at least one hour in advance of reporting time, but normally two hours ahead. These calls can come at any time. The maxi- mum number of consecutive hours an employee in the U.S. railroad train service may actually be on duty in a 24-hour period is 12 hours, and the minimum time off duty between work assignments is 8 hours, but there are no required rest days. If the crew works 8 to 12 hours, they are required to then have 10 hours off duty. This results in some crew members not being permitted to report for duty when a run is scheduled. Thus, there are "extra-boards," normally engineers with less seniority, on call to take trips. Crews with required rest and sufficient seniority can bid on any job. Local runs and passenger trains have more predictable schedules, and these trains, like the tank crews, have an average degree of team integrity. For example, passenger train crews typically work approximately 2 1/2 consecutive hours; freight train crews may work on trips that last anywhere
ANALOGOUS SYSTEMS 35 from 4 to 20 hours or more with a 2- to 3-hour rest in the middle of the trip (Michaut and McGaughey~ 19721. These short-run crews are trained for a specific territory, and they can probably be trained for certain response procedures. The National Transportation Safety Board has made the recom- mendation that the railway industry needs to (1) regulate the hours of work and compulsory rest; (2) standardize work schedules; (3) improve control over noise, temperature, vibration, etc.; and (4) evaluate, monitor, and maintain employee health (Belanger, 19891. Although there are strict requirements concerning duty schedules, codi- fied in the Hours of Service Act, at present it is not possible to mandate sleep periods; nor would such a mandate necessarily be effective. When employees are off duty, the railway industry cannot regulate what they do, and some workers may have very few hours of sleep before going on duty. As discussed in previous sections and in Chapter 5, these irregular sched- ules can have serious effects on circadian rhythms and job performance (Smiley, 19901. In the railway industry, irregular schedules have been cited in numerous investigations as a contributing factor to railway accidents (National Transportation Safety Board, 1985b, 1989; Smiley, 1990~. One report notes (National Transportation Safety Board, 1989b:2~: The changing nature of railroad operations and competitive factors have materially increased the relative number of train crew members who must work irregular and unpredictable shifts on a long-term basis. Lacking proper training and education in the physiology of fatigue, many may al- low themselves to become chronically deprived of sleep, and develop phys- iological problems that could adversely affect their performance and the safety of train operations. Other transportation industry operators are ex- posed to shift work, but the work and rest cycles of railroad extra-board and pool train crews are often more irregular and unpredictable. When a transition occurs (in this case, the train crew determines that an accident is going to occur or can occur unless some immediate action is taken), the structure of the event is moderately predictable and, to a small extent, so is the nature of the required action. If a collision is about to occur, the emergency brakes are probably applied; however the degree of application, etc., will be affected by the makeup of the train, the environ- ment (e.g., whether there is a grade), etc. It appears that the coordination factors or individual cognitive factors are of a different criticality than is the case with other teams, such as the tank crew. There is little risk to the train crew in the pretransition period and during the transition. However, there is moderate to high personal risk in the post-transition period. The train crew is highly autonomous. It receives dispatch orders, ob- serves signals and responds accordingly, regulates the speed of the locomo- tive, and so forth. There is communication via portable radios between the
36 WORKLOAD TRANSITION cab crew and any train personnel who may be in trailing units of the train (i.e., the rear brakeman if there is a 4- or 5-person crew, or the conductor). There is communication between the train dispatcher and the engineer; however, according to Smiley (1990), the dispatchers are not required to notify the engineer verbally by radio of expected meets or other conditions that may exist. This raises a number of safety issues that are similar in the tank environment. One cannot be sure of the level of situation awareness on the part of the engineer, and the dispatchers may not realize the criticality of this potential lack of awareness. Note, however, that in T. Brown's experi- ence (personal communication, 1992), there was constant communication between engineer and dispatcher, particularly with regard to meets and passes; to operate otherwise would have disastrous consequences. The environment is another feature that the locomotive cab and the tank have in common. Both are noisy, dirty, and uncomfortable (particularly the seating), vibrate, and have poor temperature control. Current design of new locomotives is focusing on ergonomically designing the seats in the cab (e.g., to provide lower-back support), insulation to reduce noise, addition of air conditioning, vibration damping, and numerous changes in information presentation. The analog dial and pointer are being replaced by more so- phisticated digital displays, and some prototypes are scheduled to be evalu- ated in 1992 (T. Brown, personal communication, 1992~. A third attribute that the rail crews have in common with the tank crews concerns the assumption that the crews are underloaded much of the time. Vigilance tasks have been viewed as minimally demanding, tedious situa- tions (Dember and Warm, 1979; Parasuraman, 1984~; however, current re search is beginning to suggest that vigilance tasks can be quite demanding and induce much stress (see Chapter 6~. Consequently, because locomotive crews, similar to armor crew members, perform tasks requiring vigilance functions, they may be stressed by the tasks that need to be completed, as well as by the environmental factors. As noted by Devoe and Abernethy (1977), the engineer is very busy, but for stretches of time, there is little stimulation. The engineer must continually monitor and anticipate changes on the trip (e.g., grades, curves, obstructions on the track) and respond when required. However, there may be long periods of inactivity ranging from 5 to 20 minutes (Michaut and McGaughey, 1972~. Unlike the tank environment, however, when a change is input to the locomotive, the response of the system is slow and complex. Thus, the two systems are, dynamically, different and therefore may require different cognitive processes of the decision makers. In summary, the locomotive and tank environments share their greatest degree of similarity in the pretransition period, and here the common themes focus more on the efficiency of the individual operator, as influenced by vigilance, stress, and sleep disruption, than on the coordination of the team.
ANALOGOUS SYSTEMS 37 NUCLEAR POWER PLANTS Nuclear power plant operators work in a control room that is very spacious, well-lit, and air-conditioned. Control rooms are supplied with potable water coolers, cooking facilities, and adjacent toilets. Operators sit in comfortable office-type chairs and are free to move around the control room. In fact, they must move about the control room to acquire the infor- mation they need to determine whether the plant is operating correctly. Information, which is acquired mostly visually, comes from hundreds of instruments arranged on rather large control panels. Nuclear power plant control rooms normally operate in a semibuttoned-up mode, in that access to control rooms is controlled by locked doors and security badge readers. Control rooms are furnished with their own atmospheric control systems, including filters for smoke, particulates, and radioactive gases. Operators of nuclear power plants, once selected, are put through an extensive training program. These operators have the equivalent of a 2-year associate degree when they complete their formal training. They are tested after completing a prescribed training program that is administered by the utility owning the particular plant for which the operator will be licensed. Individual operators are licensed at one of two levels by the Nuclear Regu- latory Commission: reactor operator or senior reactor operator. Both re- quire plant experience, but a senior reactor operator must have significantly more. All candidates for reactor operator work for some period of time in the plant operating areas as equipment operators. This allows them to become familiar with the layout of the plant and the location and operation of all equipment and systems within the it. Many nuclear power plant operators come to the industry after having served in the U.S. Navy as nuclear submarine crew members. Like crews in tanks, but unlike those in commercial aviation, teams in a given control room are typically constituted for a fairly long period of time. Prior to the Three Mile Island accident, there were no formal require- ments regarding specific nuclear power plant crew structure (other than the requirement for a specific number of crew members and their licensing level), technical support personnel and systems, or the maximum number of hours worked by crew members in any given work period. There was also no enforceable standard for individual crew members' duties during either normal or emergency operation. Many of these details have been specified since that accident. There is still, however, no federal standard for indi- vidual crew duties. Some emergency procedures are sufficiently formalized to specify each crew member's assigned duties at any point in time, but individual operators are free to deviate from procedures if they deem the procedure to be ineffective. Unlike military crews, nuclear power plant crews do not use a standard
38 WORKLOAD TRANSITION ized communication protocol. There is no equivalent in nuclear power plants to the short, understandable, and practiced protocol used by tank crews to identify targets and their location, specify armament and ammuni- tion to be used against targets, and to inform other crew members of the status of tank systems (see Chapter 10~. There is also no requirement in nuclear power plants to coordinate activities with external groups, except in certain classes of declared emergency situations. Even in these emergency conditions, a nuclear power plant control room is very much an autonomous entity. The one operational area in which nuclear power plant operating crews and tank crews differ greatly is in terms of the expectation of events that must be dealt with in a timely manner. Things do not often go wrong in nuclear power plants at least they don't go wrong to the extent that an emergency situation is encountered. Statistically speaking, nuclear power plants are very safe, at least as far as the nuclear portion is concerned. Workers in nuclear power plants are subject to the same dangers as anyone working in an industrial plant in which heavy, rotating equipment and vast quantities of high pressure steam are employed. However, no death has been directly caused by an accident in the nuclear portion of a U.S. nuclear power plant. The result of this safety factor is that nuclear power plant operating crews don't expect anything to go wrong, and usually it doesn't. The operation of a nuclear power plant, as in many process-oriented plants, is essentially a crew effort rather than an individual job, oriented toward procedural operation. As in the rail industry and the tank environ- ment, the essential nature of the job is predominantly vigilance-oriented. There are extended periods of low activity with the possibility of sudden emergency or urgent operation. Thus, the nuclear power plant industry has the same potential problems with vigilance as the rail industry. Nuclear power plant operators encounter periods of extreme cognitive underload, especially during evening and late night work shifts, followed potentially by extreme sensory and cognitive overload. If a nuclear plant is operating properly, then virtually no operator intervention is required and the crew's job becomes one of a classic continuous vigilance task complicated by the fact that the operators know the automatic monitoring systems will probably alert them if something goes wrong. One can imagine the extreme boredom and fatigue that can occur at three o'clock in the morning with everything operating smoothly, no maintenance procedures in effect, and the steady hum of the plant surrounding the control room. An operating crew working in this situation at one moment can find the whole plant going haywire the next. It has been said that things happen relatively slowly in nuclear plants and, in general, that is true. However, in the event of a major accident or equipment failure, the control room is almost instantaneously transformed into a buzzing, ringing, flashing arcade.
ANALOGOUS SYSTEMS 39 Most control rooms contain between 2,000 and 4,000 lighted-tile annuncia- tors to warn operators of specific malfunctions. These annunciators seem to work well for isolated failures in specific equipment. In any major event, however, a large proportion of these annunciators begin to flash and the alerting horns, bells, and buzzers begin to sound. The operating crew is then faced with the task of making sure the plant is being safely shut down, diagnosing the problems, and activating their emergency procedures all the while trying to acknowledge and silence the visual and auditory alarms. If a major accident does occur, it is potentially serious in terms of injury, loss of life, and property damage. It is in this transition period that another feature common to the tank and the power plant is encountered, in terms of the structure of the event. In both cases (and in contrast to railway incidents), the nature of the workload triggering event may be quite complex, imposing heavily on the operator's cognitive skills. For this reason, a heavy premium may be placed on the continuous maintenance of pretransition situation awareness: which sys- tems are working, which systems are receiving maintenance, and what is the current state of the plant. It was, in fact, failure in this regard that was partially responsible fo the Three Mile Island disaster (Rubinstein and Ma- son, 1979~. MERCHANT AND MILITARY SHIPS Historically, U.S. merchant ships consisted of three departments: en- gine, steward, and deck; however, in recent years, crew members' responsi- bilities have been reallocated and crew size has been reduced due to the implementation of automation and mechanization. Shipboard automation has had the greatest impact on the engineering department, in which a ma- jority of monitoring tasks (e.g., watch-standing) have been automated, re- sulting in a periodically unattended engine room on new vessels, while labor-intensive intermittent deck tasks have remained numerous (National Research Council, 19901. The maintenance department, whose members can perform both engine and deck jobs as well as routine maintenance, has evolved in order to facilitate a more even distribution of this labor between deck and engineering personnel. Recently built U.S. flag vessels have a typical crew size of 20 to 24, in contrast with the 40 to 45 found aboard smaller ships of 30 years ago. Similarly designed foreign flag vessels currently have crew sizes ranging from 12 to 16, and in highly automated foreign flag ships, there may be as few as 8 to 12 crew members on board. This reduction in crew size has raised the question of system safety. But in the last 20 years, as ship size has increased and crew size has diminished, there has been a concomitant worldwide reduction in vessel casualties and personnel injuries (National
40 WORKLOAD TRANSITION Research Council, 1990). Nevertheless, there are indications that this gen- eral downward trend in marine casualties may be bottoming out. There are various factors, including a worldwide aging of the merchant fleets, that could potentially lead to a reversal of this trend (W. Young, personal com- munication, 1992~. Merchant shipping operations over the past decade have been character- ized by great change in terms of technology, economics, and operating practices Applied human performance research is quite limited; much of the more complete work is dated; and the safety data that are available are incomplete, especially with regard to human performance issues (National Research Council, 1990~. Since the data and studies related to human systems have not been updated and since the commercial maritime sector is undergoing great change, broad generalizations need to be approached very carefully. Nevertheless, some insights might be available that could pro- vide general implications to high-stress human performance in other sys- tems, such as the tank environment. The vessel command structure is clearly specified: the master, or cap- tain, is in command and is responsible for the vessel at all times. When a ship approaches port, it usually is required to use an independent marine pilot who is federally or state-licensed. Typically, the pilot is placed in charge of navigation, makes maneuvering decisions, and gives maneuvering orders subject to overriding command authority of the master, who remains responsible for the safety of his vessel and crew. The master attempts to hold to a schedule and to have the ship port arrival time coincide with normal work hours of longshore labor to mini- mize overtime costs, and he tries to have short turnarounds in port to mini- mize port costs and to maximize cargo service (and payback). As in many of the other systems described in this report, including tank crews, this setup, in conjunction with watch organization, results in sleep disruption and deprivation, which often leads to fatigue and performance decrements. Coming into port, the master, third mate, and independent marine pilot (if there is one) are on the bridge, and the chief mate and second mate are involved in preparing for cargo operations. The second mate usually keeps watch during the graveyard shift (midnight to 4 am), and the chief mate has the 4 to 8 am watch; therefore, for the master and mates, there is limited rest time prior to entering port. Note that the chief and second and third mates supervise cargo operations, which are intense and also expose them to hazards during transhipment. Crew integrity also varies among the different types of ships. Non- union U.S. tankers have the greatest continuity and, among U.S. union tank- ers, the master and chief engineer usually remain with the ship for repeated trips; however, the chief mates and first assistant engineers may be reconsti _
ANALOGOUS SYSTEMS 4 l tuted for each trip (Pollard et al., 1990~. A National Research Council (1990:34) report found that "all operators "surveyed] agreed that continuity of service by crew members is an important safety factor, particularly with sophisticated shipboard systems requiring intimate knowledge. Repeated service aboard the same vessel ensures familiarity with the equipment and promotes teamwork. Continuity is most desirable among key personnel (master, chief engineer, chief mate, and first assistant engineer), and is helpful with junior officers and unlicensed personnel as well." Tank crews, thus, appear to have greater team integrity than current U.S. ships, but it is highly desirable in both environments. The military and merchant bridges are characterized by a fairly well- established structure for decision making and information flow. In the Navy, Coast Guard? and on other military vessels, communications is highly structured. The roles in merchant marine are reasonably well established for masters, mates, and pilots, but there is a considerable range of interpre- tation for their interaction; it is more a judgment call for the master and pilot. Teamwork is an essential part of professional development in the military; in the merchant marine setting, teamwork is taught in maritime schools and is expected aboard the ship within the general structure and role models exist, but the actual level of bridge team interaction is variable and generally consistent across the wide category of vessels. The situation is different for tugs because there is usually only one person in the pilot house. Shipping, similar to other freight transportation modes, is often charac- terized by longer-than-average work weeks, nonstandard work days, inter- mittent extensive night operations, and periods of intense effort preceded by periods of inactivity (Pollard et al., 1990~. Scheduling factors frequency of port calls, operation in congested waters, arrival and departure times, long duty tours (especially those that exceed 75 days), and less time avail- able to go ashore all affect the fatigue (due to interference with crew members' sleep and circadian rhythms) and stress felt by crew members. Fatigue and excessive workload were determined to have been contributing factors in a number of marine accidents (e.g., National Transportation Safety Board, 1988a, 1990~. Work-rest schedules are affected by the type of work being performed, and workload and shipboard operations vary drastically, depending on the stage of the voyage. Workload is extremely high during mooring, cargo operations, and unmooring and is quite reduced in transit, during which time many maintenance tasks are performed. The negative effects of these schedules or performance following the transition are similar to those docu- mented in other environments and suggest that crew work-rest schedules must be carefully planned. In addition, "Aboard merchant ships, current
42 WORKLOAD TRANSITION manning statutes as interpreted by federal courts set no upper limit on the hours a crew member may work" (National Research Council, 1990:75~. This adds to the potential for safety-related incidents. As in the rail industry and the tank environment, communications is a critical issue whose importance cannot be overemphasized. Merchant ves- sel operations are not conducted in a highly structured decision-making environment. Interactions lack the precision and protocols associated with military operations, tending instead to be more informal and ad hoc. A1- though there are self-enforcing international rules to prevent collisions at sea, they are designed to guide the interactions of two vessels. The rules become ambiguous when more than two vessels are involved, as frequently occurs in ports and waterways. Meeting and overtaking situations are char- acterized by informal coordination using voice radio rather than guidance by strict maneuvering protocols. Traffic regulation comparable to that in the aviation sector is not practiced, although interactive information sharing is available for some ports and waterways in the form of Vessel Traffic Services (VTS) (Ives et al., 1992~. Although human error is often cited as a factor in marine casualties, marine accident investigations primarily focus on proximate human causes of accidents rather than more subtle factors that underlie human perfor- mance. However, beginning in May 1992, the U.S. Coast Guard imple- mented the Marine Investigation Module (MINMOD), a greatly expanded data base, that focuses on human factors and human performance issues in marine casualties (S. Sheek, personal communication, 19921. Successful military operations rely heavily on effective human perfor- mance of crews and task groups or forces operating cohesively as a single entity, even with modern warfighting technology. Individuals, individual ships, and combinations of units are expected to function effectively and efficiently, with precision and without hesitation. At the same time, reason- able flexibility for innovative and creative decision making is retained to accommodate the variabilities in the combat scenarios, with flexibility vary- ing by the role and responsibility of each individual. The teamwork that is required itself requires that good order and discipline be established in the individuals throughout the organization. It also requires highly stylized operating standards and protocols. Well-defined authority is embedded in a hierarchical command structure to establish both a decision making and performance structure that can function effectively under the stress of time- critical situations. Effective teamwork is achieved through technical train- ing of individuals through resident schools, short courses, and correspon- dence courses and by extensive, frequent, on-site training and drills. This approach concurrently accommodates the transfers that occur, prepares indi- viduals to work effectively singly and as a unit team member, and estab- lishes in each team member the time phasing required to respond instinc
ANALOGOUS SYSTEMS 43 lively under the pressure of high-stress operating conditions. The roles and responsibilities of individuals are continuously reinforced throughout the military organizations as a routine practice for professional and interper- sonal relationships, thereby maintaining well-defined command relationships. The operation of military ships while in company is characterized by high levels of precision. There are well-defined maneuvering schemes and execution protocols. Fleet maneuvering protocols are established in opera- tional instructions and routinely practiced. The naval approach works well aboard individual units and for convoy operations. However, there are exceptional differences between what is found in a naval task force or group and what is found in the interaction of ships in the nonmilitary setting, particularly in ports and waterways. When military ships interact with merchant shipping, especially in confined harbors and waterways, associ- ated human interactions devolve to a much less precise and largely informa decision-making structure. Some port-state nations have established VTS to improve order and predictability in waterway interactions. These capabilities are essentially interactive information sharing communications networks with, in some cases, very limited positive control. A VTS, in effect, places a decision-making structure within the existing informal decision-making network that charac- terizes the marine operating environment. There are about 200 VTS facili- ties worldwide of varying capabilities; approximately 20 are located in the United States, some of which are operated by the U.S. Coast Guard and others are operated by the U.S. Army Corps of Engineers, other governmen- tal organizations, and marine pilots (Ives et al., 1992~. It is believed that the use of a VTS will improve the accuracy and completeness of information and that, given this information, operator deci- sion making will be improved. However, this depends on the relevance and accuracy of the communications on a single vessel, between vessels, or between a vessel and a VTS. There are substantial differences in communi- cations between the military and maritime settings. In the Navy, internal as well as external communications are critical to successful warfighting. There are very precise standards and protocols for internal communications; exter- nal communications have been greatly improved by the composite warfare commander (CWC) concept by means of satellite down links, electronic means, etc. There are precise communications protocols for vessel interac- tions, but the protocols on the bridge are less precise. In the merchant marine setting, although the roles of each individual on the ship bridge are well understood, how the members communicate varies greatly. Bridge crew communications tends to be much more informal, lacking the well-defined protocols and stylized language found in the Navy. Where there is a VTS, circuit discipline is enforced, especially when oper- ated under military protocol. Military protocols are routinely employed in
44 WORKLOAD TRANSITION VTS to ensure the clarity, brevity, and accuracy of the information ex- change. Bridge commands are relatively well defined, standardized, and universal. Communications in maritime are voice VHF radio. This in- volves bridge communications (i.e., intrabridge communications) but not bridge-to-bridge communications (i.e., interbridge or intervessel communi- cations), which has been identified as a contributing factor in at least one marine accident (National Transportation Safety Board, 1984~. Automatic radar plotting aids (ARPA) used by ships are capable of tracking and displaying the courses of a large number of targets automati- cally and of generating warnings regarding possible collisions in open water transits. These collision avoidance features are of marginal use in confined waterways and in situations where frequent maneuvering is required. How- ever, in some situations this aid is one means of minimizing the possibility of collisions and groundings. A somewhat dated review report has identified a set of prevailing con- ditions typically found at the time of many marine accidents (National Trans- portation Safety Board, 1981:183: the ships were outside an active vessel traffic service (communication control center) area, radar was not in opera- tional use, there was no equipment failure, and the occurrence was during the 4 am to 8 am watch in clear visibility on a U.S. waterway on which the inland navigation rules were in effect. "The Safety Board found that inef- fective communication was either a causal or a contributing factor in 7 out of 33 collisions. VHF communication problems ranged from the failure to keep a listing watch to the failure to transmit timely navigational intentions to the lack of a VHF communication requirement." Watchkeepers at the vessel traffic center acquire, interpret, and distrib- ute system-wide navigational information. VHF radio is the standard for marine communications. A single frequency is used for communications in each VTS sector, and a designated frequency is available for direct bridge- to-bridge communications between vessels (National Research Council, 1990~; however, contact is not always established to confirm maneuvering Intentions. Characteristics of the physical environment, including noise levels and vibration, also vary from ship to ship. But in general it appears that, similar to the tank environment, these factors are present and may, unbeknownst to the crew, add to the stress already felt, although their magnitude tends to be somewhat less than in the tank. As noted by Pollard et al. (1990), ship crew members believe they adapt to these noise levels and, therefore, they be- lieve their performance is not affected by this environmental stressor. How- ever, as in the tank environment, sound (or changes in sound) can also be an important task relevant cue; in this case, it may be important for maneuver- ~ng purposes. The ship is a complex system with many components related to com
ANALOGOUS SYSTEMS 45 partments, hatches, fuel, and cargo locations, as well as weather, sea, and land characteristics that influence its ability to withstand damage. Hence, the structure of the event may be ill-defined, and the time constant may vary. If situation awareness of this state is absent in a pretransition period, disaster may result. For example, if a grounding or collision occurs in a confined waterway, the time constant may be short, and unpredictable re- sponse types may be required. However, for an accident in open water during transit, the time constant is longer and the response types may be more predictable. NATURAL DISASTERS Emergency workers who are responding to a natural disaster constitute a normal population working under abnormal conditions. Floods and hurri- canes usually are preceded by a buildup that allows time for warning and subsequent preparation for impact. Major aircraft disasters, explosions, earthquakes, or tornadoes typically allow far less preparation for the spe- cific event. For the first 2 weeks following the occurrence of a major disaster, Red Cross staff members work 12 to 14 hour days. After the second week, they get half a day off. Individuals who are on a disaster assignment for 2 or 3 months may get 1 day off after the third week (Eby, 1985). The core resources of the team already exists, and volunteers are incor- porated into the system. Although central planning should focus on ways to effectively allocate human and material resources, the allocation decisions, themselves, are made without much preplanning (Dynes, 1989~. Training of as much of the team as possible in simulated disasters appears to be a necessary precondition for effective disaster management (Rolfe, 1989J. The probability of a natural disaster occurring varies, depending on location; however, even in an area in which it is most expected (e.g., earth- quakes in California), the probability of occurrence is still quite low. The response to the event is predictable; however, the decisions that need to be made will be unique. The decision making is decentralized and pluralistic, and the team, similar to the tank crew, must coordinate and cooperate with many other groups and teams to be most effective. The physical conditions of the environment are typically poor, due to the nature of the event, but the extent to which the team is exposed to risk of personal injury is minimal following the disaster. The environment dur- ing a natural disaster is similar to that of the tank crew engaging in battle, in that people attempt to protect themselves inside buildings, etc., during the natural disaster just as tank crew members in battle remain buttoned up in the tank. Immediately following the natural disaster, however, when the relief teams are working, many team members are out in the open with little
46 WORKLOAD TRANSITION protection from the elements. The environment, although different, leaves much to be desired. As can be ascertained, teams in this environment are similar to tank crews in that their sleep schedules are similarly disrupted, the stress is somewhat comparable (although the response period following the transi- tion is much longer for teams responding to the natural disaster), and the team must coordinate with others to accomplish its goals. While the nature of the response to disasters is, in many respects, quite different from the tank environment, it is noteworthy that this is one of the few transition team situations that has received systematic study (Dynes, 1989~. The author's conclusion in the study indicated that the teams involved were in fact quite effective in their response. EMERGENCY MEDICAL SERVICES Emergency medical service (EMS) helicopter crews (also called medevac- medical evacuation) consist of a pilot and a critical care medic; EMS ambu- lances operate with a 2-person or sometimes a 3-person crew a driver and 1 or 2 medics. These medics are recertified every year on practical and written cardiopulmonary resuscitation techniques. Upon arrival at the scene of the event, the medicos) performs an assessment of the level of injury, following a set protocol that dictates beginning with an assessment of the head and neck, then of the chest, the groin, the legs, and finally the feet. The medic checks the vital signs and the eyes, then decides where the patient will go and consults with the doctor at the chosen location. The consulting doctor is the one who will care for the patient when he or she arrives at the hospital; however, this doctor may later turn the care of the patient over to another doctor. The medics communicate using written and oral protocols. During the assessment, medics go through a process of pattern matching. In addition, medics, like tank crew personnel, must be concerned about self-preservation, their personal safety, and what to do if there is a hostile environment. In the 1960s and early 1970s, emergency medical services were used almost solely to transport injured patients as quickly as possible to the nearest hospital. The first commercial EMS helicopter program in the United States started in 1972, and commercial EMS helicopter activity has in- creased sharply since 1980 because some "surgeons began to suggest that accident victims would fare better if they were taken to larger hospitals that had all the necessary manpower, equipment, and supplies close at hand. The surgeons produced statistics to prove that accident victims survived more often at large hospitals than at small ones" (Doelp, 1989:59~. As a result, many patients were being transported to hospitals that were not near the accident scene. This generated a need for patient transporters to be
ANALOGOUS SYSTEMS 47 specially trained to begin treating the injured before reaching the hospital, because what happens during the first hour after the onset of the injury (coined the Golden Hour) is critical to the probability of the patient's sur- vival (Franklin and Doelp, 1980~. The EMS crew is usually on the way to the scene of the event in a matter of minutes, and once on the scene the injury assessment occurs as soon as possible depending upon the location of the patient (e.g., if there has been an automobile accident, when the medics can physically get to the patient to perform the assessment), but usually within a few minutes. The average number of calls the EMS crews respond to each year is dependent on the environment. It is not uncommon for an ambulance crew in a suburban area to average 2,300 calls in a year (which is an average of almost 200 calls per month or approximately 6.5 calls per 24-hour period) (Maryland State Firemen's Association, 1991), although the number of calls may vary from 500 to 4,000 or more calls per year depending on the subur- ban location. At this level, the crews should always be prepared for incom- ing calls. However, in a rural area, they may average one-fifth to one-tent this number of calls, which would result in one call every 20 to 25 hours, on average (Maryland State Firemen's Association, 1991~. Although not as great a probability of occurring, rural EMS crews still have a high expect- ancy of a call coming in each day. None of the crews can anticipate when these will occur; however, when storms are in the area or a fire has been called in, the likelihood of a medical emergency is greater. The length of duty for EMS crews varies depending on the type of organization they work for. For example, volunteer ambulance crews some- times schedule duty, but unlike paid ambulance crews, this staffing may not be active 24 hours each day. These paid ambulance crews work normal 8- hour shifts, which may be extended depending on the requirements of the situation. EMS helicopter crews work on shift schedules, and the greatest number of calls are received at night, many times in bad weather (which may be one of the contributing factors of the accident that generated the need for medical services in the first place), and their mission requires landing and takeoff from unimproved landing areas. The pilot must receive 10 consecutive hours of rest in any 24-hour period if the combined duty and rest periods total 24 hours. Each flight crew member must have 13 rest periods of at least 24 consecutive hours every 90 days. The EMS helicopter pilot must have 8 hours of consecutive rest every 24 hours and 10 hours of consecutive rest before reporting to the hospital for availability for flight time. An EMS pilot may not be on duty longer than 72 hours (Doelp, 1989~. It is interesting to note that, according to Doelp (1989:36), "The majority of EMS pilots responded that next to combat flying, the EMS flight environment is the most stressful and challenging." This may be attributable to the fact that, in addition to poor environmental conditions,
48 WORKLOAD TRANSITION the EMS helicopter pilot and crew must respond quickly, often do not have the time to plan the flight, and must make decisions knowing that human life is at stake. The probability of the EMS helicopter crashing is nearly twice that of other noncombat helicopter operations (National Transportation Safety Board, 1988b). Of the 59 EMS helicopter accidents in the National Transportation Safety Board's data base between May 1978 and December 1986, 18 were weather-related. Of the 18, 15 involved reduced visibility and spatial dis- orientation and occurred below 1,200 feet in uncontrolled airspace; the re- maining 3 accidents resulted in hard landings due to heavy winds. Thus, the risk of personal injury or death to the EMS helicopter crew is greater than for either other helicopter crews or for EMS ambulance crews. The continuity of the crew in the EMS ambulance crew, again, is de- pendent on the organization. In paid companies, the crew remains the same approximately 75 percent of the time; in volunteer companies, the crew could change with every call, but the individuals usually know each other. There is a thin level of hierarchy in commercial EMS. The crew may be responsible only to themselves and the protocol, but EMS ambulance crews that belong to a firefighting company may have a thicker level of hierarchy, which may extend from the battalion chief down. The medics for the first few minutes may function alone, but as soon as the assessment has been made and a hospital chosen, the medics will be in almost constant commu- nication with a doctor at that hospital or center. All services performed from then on will be done in coordination with the waiting doctor. Crews in this system are similar to tank crews in a few major respects. First, duty schedules have been identified as having an influence on the probability of success; and the sharing of information is essential. If the EMS helicopter is flying at night and in bad weather, the risk of personal injury is realized, but not as greatly as a tank crew entering battle. Finally, as discussed in Chapter 7, the issue of navigation and geographic orienta- tion is critical in both environments. TRAUMA CENTERS AND EMERGENCY ROOMS Trauma center and emergency room teams consist of doctors, nurses, and an anesthesiologist, prepared to care for injured patients who are brought to the center or hospital for treatment. The exact composition of the medi- cal team is determined by the operating procedures of the trauma center or hospital, and their requirements vary depending on the community in which they operate. For example, at Children's Hospital National Medical Center in Washington, DC, the nucleus of the trauma team consists of the trauma coordinator, the surgical resident, the resident in the intensive care unit, the nurse in charge, and at least one other nurse. This team is assisted by a
ANALOGOUS SYSTEMS 49 support group that includes an X-ray technician, lab technicians, blood bank technicians, and a social worker (Doelp, 1989~. Time is probably the most critical element in medical services. In recent years, surgeons have come to realize that the first hour of treatment is critical to the patient's recovery (Franklin and Doelp, 1980~. The crisis transition or event (i.e., treatment of an arriving injured patient) unfolds in a matter of seconds and minutes. There is a great probability that one or more patients will arrive during the team members duty period, and the team members will work long hours. Like EMS teams, adult trauma centers (such as the Maryland Institute for Emergency Medical Services known as Shocktrauma), pediatric trauma centers (such as the Children's Hospital National Medical Center), and emergency rooms in hospitals around the country maintain a fairly continuous level of preparation for patients or accident victims that can be expected at any time. Often the trauma centers receive only a few minutes advance notice that a patient is on the way. During this time the hospital or trauma center and its team members must be notified by a communications center (such as SYSCOM for Shocktrauma and ECIC the Emergency Communications and Information Center for Children's Hospital). The team members then converge on the arrival, code, or emergency room to prepare for the arriving patient. The hospital teams, especially in the trauma centers, are on duty much longer than teams in many other environments. The medical teams in the Children's Hospital National Medical Center are on call one day out of three; and according to Doelp (1989), for the day the resident is on call, he or she must stay at the hospital all night to be available to the nursing staff. If there are no problems, the resident may sleep, but this is a rare occasion. The off-call day is a normal workday, which includes two sets of rounds (one morning and one evening) and a full day in the operating room. Work- days usually last longer than 12 hours. The surgical residents get one day off every other weekend. Each trauma center and hospital have different schedules, but they are similar in nature. Hence, it is undoubtedly the case that sleep disruption is often present in emergency room personnel, al- though the extent to which this has had deleterious effects on performance has not been well documented. The event is relatively predictable. According to Doelp (1989:78-9), "Trauma medicine is, first and foremost, checklist medicine [a treatment protocol]." This means that there is a written set of procedures that are to be followed for each patient. The checklist is the same as that described above for emergency medical services. A series of tests are conducted to determine the type and extent of injury to each area instead of treating injuries in a nonrational order in which certain symptoms could easily be missed or overlooked. The environment in treatment or emergency rooms, unlike that of the
50 WORKLOAD TRANSITION tank, is cool (often between 65° and 69° F), there is much lighting, and much of the noise comes from the medical team and the patient, if he or she is conscious and feeling pain; however, the room is not inherently noisy. At times, there may be some problem with cramped working space, but this cannot be avoided, in that all members of the team may be working on the patient. The treatment or emergency room itself may be quite spacious. Until recent years, the team probably would not have been considered to be at risk of personal injury. But with the outbreak of AIDS and the amount of blood that may be found, especially in the treatment room of the trauma center, the team is at a much greater risk of exposure to personal injury. The team may therefore feel the stress of risk. Trauma center and emergency room teams have a low chain of com- mand. In emergency rooms around the country, nurses follow the directives given by the doctors, and technicians and others in the support group follow the directives of the nurses. At Shocktrauma and Children's Hospital, un- like most hospitals around the country, nurses have almost as much author- ity as the doctors. At Children's Hospital, the trauma coordinator is in charge of what is happening in the treatment room, and the nurse in charge supervises the emergency room nursing staff. The members of the team in the emergency room interact with their support group outside the room to have X-rays taken, receive additional units of blood, have tests conducted on blood samples taken, etc. The core team cannot work in isolation; it must coordinate with other teams and individuals to be successful in its . . mission. The residents who work on these teams go on rounds with the chief resident, who reviews each patient's status, progress, and treatment. In addition, the work in the emergency rooms is reviewed by the trauma center director or an assistant, and problems that have been identified are dis- cussed with the appropriate team members. While working in the emergency rooms, the medical teams have a high level of integrity- they work closely together and on similar duty sched- ules. There appears, however, to be a large rate of turnover of personnel in emergency rooms, especially in the trauma centers, possibly due to the high level of stress inherent in the job. This reduces the amount of team continu- ity that would otherwise be achieved and increases the on-thejob training that is necessary. CAUTIOUS GENERALIZATIONS From this discussion of the analogous systems of interest, a few conclu- sions can be extended to the tank environment. First, in each system, appropriate duty schedules are of utmost importance. At present, these appear to be lacking in maritime, railroad, and trauma center systems, to
ANALOGOUS SYSTEMS 51 name but a few. In most of these systems this factor has been identified as contributing to numerous accidents. As discussed in Chapter 5, if work-rest schedules were employed that are synchronous with the circadian rhythm, fatigue and possibly stress levels would be reduced, resulting in better re- sponses to transitions and, in some cases, fewer system transitions. Second, lack of a communication protocol appears to have serious con- sequences on crew performance. Many crews operate in more isolation than would appear prudent Railway crews as well as a number of ship crews, if they had been given more verbal information from the dispatcher or communications center, may have prevented the accidents that occurred. Tank crews must communicate with other crews to increase the probability of successful mission completion; however, as discussed in upcoming chap- ters, other factors interfere and cause confusion and miscommunication. This miscommunication has also occurred in a number of maritime acci- dents. If some of these analogous systems, like the tank crews, had a standardized terminology and protocol, miscommunication could be reduced and the likelihood of accidents would also diminish. When the triggering event is complex or unstructured, then strong support for continuous situa- tion awareness the state of the system and environment in the pretransition period will be likely to support more efficient and adaptive problem solving during the transition. Although this section has focused on what these analogous systems have to offer to the tank environment, one could also ask what conclusions drawn in the tank environment can be generalized to these other systems. Such conclusions emerge from our discussions in the following chapters and are integrated in Chapter 13. Next we examine workload factors and stressors that affect performance during the transition as well as processes that are inherent in transition. REFERENCES Belanger, J.D 1989 Railway safety. CurrentIssue Review. Canada: Library of Parliament. Dember, W.N., and J.S. Warm 1979 Psychology of Perception, Second Edition. New York: Holt, Rinehart and Win ston. Devoe, D.B., and C.N. Abernethy 1977 Maintaining Alertness in Railroad Locomotive Crews. Transportation Systems Center, U.S. Department of Transportation. Report No. FRA/ORD-77/22. Wash ington, DC: Federal Railroad Administration. Doelp, A. 1989 In the Blink of an Eye: Inside a Children's Trauma Center. New York: Ballantine Books. Druckman, D., and R.A. Bjork, eds. 1991 In the Mind's Eye: Enhancing Human Performance. Committee on Techniques
52 WORKLOAD TRANSITION for the Enhancement of Human Performance. Washington, DC: National Acad emy Press. Dynes, R. 1989 Community Emergency Planning: False Assumptions and Inappropriate Analo gies. Paper presented at the Workshop on Safety Control and Risk Management. Karlstad, Sweden: Swedish Rescue Services and World Bank. Eby, D.L. 1989 A disaster worker's response. Pp. 119-125 in Role Stressors and Supports for Emergency Workers. Rockville' Maryland: U.S. Department of Health and Hu man Services. Foushee, H.C., and R.L. Helmreich 1988 Group interaction and flightcrew performance. In E. Wiener and D. Nagel, eds., Human Factors in Aviation. San Diego, California: Academic Press. Franklin, J., and A. Doelp 1980 Shock-Trauma. New York: St. Martin's Press. General Accounting Office 1992 Engineer Workshift Links and Schedule Variability. Report No. GAO/RCED-92- 133. Washington, DC: U.S. General Accounting Office. Graeber, R.C. 1988 Aircrew fatigue and circadian rhythmicity. Pp. 305-344 in E. Wiener and D. Nagel, eds., Human Factors in Aviation. San Diego, California: Academic Press. Ives, P.L., Jr., W. Parker, F. Seitz, and W. Young 1981 1984 1985a 1992 Assessment of Vessel Traffic Services. Unpublished background paper prepared for the Marine Board, Committee on Advances in Navigation and Piloting. Ma- rine Board, National Research Council. Maryland Sate Firemen's Association 1991 Maryland State Firemen's Association 1991 Statistical Report. Michaut, G.M.E., and T.P. McGaughey 1972 Work Conditions and Equipment Design in Diesel Locomotives: Feasibility Study and Recommendations. Canadian Institute of Guided Ground Transport. Canada: Queen's University. National Research Council 1990 Crew Size and Maritime Safety. Committee on the Effect of Smaller Crews on Maritime Safety, Marine Board, Commission on Engineering and Technical Sys- tems. Washington, DC: National Academy Press. National Transportation Safety Board 1980 Aircraft Accident Report Air New England, Inc., deHavilland DHC-6-300, N383EX, Hyannis, Massachusetts, June 17, 1979. Report No. NTSB/AAR-80/1. Washing ton, DC: Bureau of Accident Investigation. Special Stud~Major Marine Collisions and Elects of Preventive Recommenda tions. Report No. NTSB/MSS-81/1. Washington, DC: Bureau of Technology. Sinking of the U.S. Tug #2 While Assisting in the Docking of the USS William V. Pragg, Pensacola, Florida, October 12, 1983. Washington, DC: National Trans portation Safety Board. Aircraft Accident Report US Air, Incorporated Flight 183 McDonnell Douglas DC9-3I, N964VJ, Detroit Metropolitan Airport, Detroit, Michigan, June 13, 1984. Report No. NTSB/AAR-85/01. Washington, DC: Bureau of Accident Investiga tion. 1985b Railroad Accident Report Head-On Collision of Burlington Northern Railroad Freight Trains Extra 6714 West and Extra 7820 East at Wiggins, Colorado, April 13, 1984 and Rear-End Collision of Burlington North Railroad Freight Trains
ANALOGOUS SYSTEMS 53 7843 East and Extra ATSF 8112 East Near Newcastle, Wyoming April 22, 1985. Report No. NTSB/RAR-85/04. Washington, DC: National Transportation Safety Board. 1987 Aircraft Accident Report-Midair Collision of Nabisco Brands, Inc., Dassault Fal con, DA50, N784B and Air Pegasus Corporation, Piper Archer, PA28-181, N1977H, Fairview, New Jersey, November 10, 1985. Report No. NTSB/AAR-87/05. Washington, DC: Bureau of Accident Investigation. 1988a Collision between the USS RICHARD L. PAGE (FFG-5) and the U.S. Fishing Vessel CHICKADEE, the Atlantic Ocean, April 21, 1987. Washington, DC: Bu reau of Accident Investigation. 1 988b Safety Study~ommercial Emergency Medical Service Helicopter Operations. Report No. NTSB/SS-88101. Washington, DC: National Transportation Safety Board. 1989a Railroad Accident Report Head-End Collision of Consolidated Rail Corporation Freight Trains UBT-506 and TV-61 near Thompsontown, Pennsylvania, January 14,1988. Washington, DC: National Transportation Safety Board. 1989b Safety Recommendation. Letter Report Dated May 12, 1989. Washington, DC: National Transportation Safety Board. 1990 Marine Accident Report~rounding of the U.S. Tankship EXXON VALDEZ on Thigh Reef, Prince William Sound, near Valde, Alaska, March 24, 1989. Report No. NTSB/MAR-90/04. Washington, DC: Office of Surface Transportation Safety. Parasuraman, R. 1984 The psychobiology of sustained attention. Pp. 61-101 in J.S. Warm, ea., Sustained Attention in Human Performance. Chichester, UK: Wiley. Pollard, J.K., E.D. Sussman, and M. Stearns 1990 Shipboard Crew Fatigue, Safety, and Reduced Manning. U.S. Department of Transportation, Research and Special Programs Administration. Report No. DOT- MA-RD-840-90014. Washington, DC: Office of Technology Assessment. Rolfe, J.M. 1989 The end-of-flight simulation. In D. Mangelsdorff, ea., Proceedings of the 7th User Stress Workshop. Consultation Report No. 91-0001. Washington, DC: U.S. Army Health Services Command. Rubinstein, T., and A.F. Mason 1979 The accident that shouldn't have happened: An analysis of Three Mile Island. IEEE Spectrum 16:33-57. Smiley, A.M. 1990 The Hinton train disaster. Accident Analysis and Prevention 22(5):443-455. Wickens, C.D. 1992 Engineering Psychology and Human Performance. New York: Harper Collins. Wickens, C.D., and C. Kessel 1981 Failure detection in dynamic systems. In J. Rasmussen and W. Rouse, eds., Hu- man Detection and Diagnosis of System Failures. New York: Plenum Press. Wickens, C.D., R. Marsh, M. Raby, S. Straus, R. Cooper, C.L. Hulin, and F. Switzer 1989 Aircrew performance as a function of automation and crew composition: A simu- lator study. Proceedings of the Human Factors Society 33rd Annual Meeting. Santa Monica, California: Human Factors Society. Woods, D.D. 1988 Commentary: Cognitive engineering in complex and dynamic worlds. Pp. 115- 129 in E. Hollnagel, G. Mancini, and D.D. Woods, eds., Cognitive Engineering in Complex Dynamic Worlds. London: Academic Press.