|
Items in cart [0] |
Questions? Call 888-624-8373 |
PAPERBACK PDF BOOK Free Resources |
||||||||||||||||
|
||||||||||||||||
|
|
|||||||||||||||
| ||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 28
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
OCR for page 29
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
OCR for page 30
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.
OCR for page 31
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.
OCR for page 32
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
OCR for page 33
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;
OCR for page 34
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
OCR for page 35
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
OCR for page 36
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.
OCR for page 37
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
OCR for page 38
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.
OCR for page 43
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
OCR for page 44
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
OCR for page 45
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
OCR for page 46
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
OCR for page 47
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,
OCR for page 48
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
OCR for page 49
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
OCR for page 50
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
OCR for page 51
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
OCR for page 52
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
OCR for page 53
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.
Representative terms from entire chapter:
transportation safety
