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ee ene ee

TABLE XiX. Comparison of Average Number of Hours Slept
in: Connection With the Var
on the Two Rotation Schedules~Survey ©

ious Shifts (and Days Off)
£ ARTCC ATCSts

Rotation Schedule

shite
5-Day _. 2-2-1

Day 6.0 5.84

Evening 1b 1.6

Mid 5.2 3.5 #e

Days Off 17 7.9 : :
Average, 5-Day Workweek 6.4 6.1 ** :
Average, 7-Day Week 7 2.0

* p< .05

te p< 01 i

32



\

\
i
‘3
'
j
F
Hy

Studies were carried out at Atlanta (ATL) and Fort Worth (FTW) Air Route
Traffic Control Centers (ARTCC) to examine further the relationship of stress to
shift-rotation pattern. ATL was on the straight-5 shift pattern and FTW, was: on
the 2-2-1 (13). These two ARTEC's were chosen for comparison because of several
similarities, thus reducing the variables that might enter into differences in
stress. They have similar climates, size, traffic loads, and relationships to
the cities for which they are ucmed.

Twenty-three male ATCS's at Aij. and 29 at PIW volunteered to setve as
subjects. ‘Twenty-three of the FIW controllers were on the 2-2-1 rotation schedule
and six were on the straight-5 pattern. Data on the 23 FTW controllers on the
standard 2-2-1 pattern were compared with data from ATL controllers on the straight~5
rotation.

Pooled urine collections were made by every subject throughout each 8-h
work period for one S-d workweek. Controllers at ATL made urine collections on the
game shift for 5d. Seven ATL subjects were on the midshift, seven were on the day
shift, and nine were on the evening shift.

At FIW, because of. the daily change.of work periods, urine ‘collections
were made on more than one shift’ by each of the 23 subjects on the 2-2-1 pattern.
Ten FIW controllers worked all three shifts (day, midshift, and evening) and 13
worked days and evenings only.

Subjects at both facilities collected urine in the manner previously
described.

Physiological stress among FIW controllers is measurably less than among
ATL controllers (Fig. 2). Since the FIW ARTCG was on the 2-2-1 rotation schedule
it ie clear that, in and of itself, there is no physiological support for the con-
viction that the 2-2-1 schedule is more taxing than the 5-d schedule to the indi-
vidual controller. However, it would be equally unjustifiable to consider the
2-2-1 schedule necessarily--or always--superior to the 5-d schedule. Operationally
important differences probably are minimal.

Table XVII shows the comparison of resting and working values for st, e,
and we at ATL and FIW. There were no significant differences in e excretion during
sleep between the two facilities. At each of the facilities, however, 6t, €, and
ne excretion was greatest during day sleep following midshift work. Excretion of
at and ne by ATL controllers during sleep (day or night) was significantly greater
than the output of these stress indicators by FIW controllers.

Table XVII shows that e excretion during work was not significantly dif-
ferent on any shift at ATL and FTW. Excretion of ne was significantly higher at
ATL than at FIW on all three shifts. However, st excretion on the day and evening
shifts was significantly higher at ATL than at FIW; the difference in st excretion
during the midshift work wes insignificant.

With regard to the amount of sleep obtained on the two schedules, the
differences again are minimal. At TAH, where essentially the same group waB studied
on the two rotation patterns, the. study showed that controllers on the 5-d rotation
slept significantly longer at night prior to day shifts than they did in the day

prior to midshifts. Tuese same ATCS"S on the 2-2-1 rotation slept significantly
28



Eight of the ATCS's had been promoted or had transferred for other
reasons to supervisory or other noncontroller jobs. Table XXI shows a comparison
of changes in urine biochemistry of those 8 with changes for 24 other ATCS's who
remained active in ATC positions. The data in the table may be summarized as
follows: (4) Most members of both groups showed decreases in st excretion
at rest and at work in the second study relative to the first study. (it) Most
members of the active controller group showed increases in é excretion at rest,
while equal numbers of noncontroller subjects showed increases and decreases in
e excretion at rest. (i1i) In: the second study most active controllers showed
a decrease in e excretion at work. Most noncontroller subjects showed increases
in e excretion at work. At rest, equal numbers of noncontrollers showed increases
and decreases in ne excretion. At work, slightly more noncontrallers showed
decreased ne excretion than. showed increases. Most active controllers showed
increases in ne excretion at rest and decreases at work.

Table XX11 shows a comparison of individual indices and C, for active
controllers and noncontrollers and the changes from first to second studies. The
st index, cet, is significantly lower in the second study than it was in the
first. For the noncontrollers, c.g is lower in the second study with marginal sig-
nificance. C, is lower in the second study for both groups because of the strong
effect that c.g, has on the average. The norepinephrine index, tye, showed no
significant change for either group.

The data in Table XXII are. shown on the Streng diagram in Fig. 12, It
is apparent that total stress is reduced in noncontrollers to a greater degree
than in active controllers. .

Because of the small number of controllers represented in this study,

+ conclusions are guarded if not tentative. With that in mind, it can be pointed

out that both groups showed a decrease in st excretion level. This finding

can be interpreted to mean that chronic stress is less in the second study than
in the first. It should be mentioned again that only five first-study facilities
are represented: ORD, IAH, and OPF ATCT's; LAX TRACON; and Miami (MIA) ARTCC.
Because all of these original facilities had comparatively high stress levels,

it is not unexpected that chronic stress of the group would be reduced when a move
was made somewhere else, but the possibility also exists that with time the job
becomes easier for some people—a counterburnout phenomenon.

An additional explanation may be based on improvement in the work eituation.
An earlier study showed that the introduction of ARTS-III was associated with a
reduction in st excretion (14). There was an interval of 5 to 9 years from the
first until the second study, a period during which many improvements were made in
the ATC system.

These ATCS's were S to 9 years older at the time of the second study,
which may also partly explain the decrease in st excretion, Reduction in st
is known to accompany the normal process of aging (5,19,23).

During the 10-year period over which these ATCS stress studies were
carried out, some of the participating ATCS's experienced various disabling medi-
cal conditions. Notations regarding these medical conditions requiring either
waiver or retirement are in the controllers’ files in the Aeromedical Certification



A battery of measurements.was chosen to describe stress because of some
degree of stressor-response specificity. The adrenal cortical response reveals
primarily chronic stressors such as labor-management conflicts, marital problems,
financial difficulties, etc. The adrenal medulla is primarily responsive to.

acute workload or stimuli that’ are iting or arousing. Ne from sympathetic
merve em Serated ma‘nly in response to physical exertion. San re

indicator of momentary events.

The volume of data from these studies made it difficult tu generalize about
the findinge in a concise and comprehensible way. It was recognized that an
index was needed that would integrate some of the measures and thus facilitate
various comparisons (12).

x was wore ated by several factors, First,

e ints
There SZ about a thousand times as much steroid material as there is of cate~
cholamines. If the assumpt’on is made that the three SIH's are equal in impor-
tance, then raw data must be treated mathematically so that their relative
importance is. expressed. After severai studies had been carried out, there were
86 many values for each SIH that the mean of each SIH was stable. Each value
divided by thie mean, termed the grand mean (Xc), was thus weighted (per unum}
go that all values for. each SIH were on a common scale.

y {

specimen. Retrospectively, it is apparent that we were too naive initially in

variation made it undesirable to use rest~to-work increments in cxcretion level
of SIH's as a stress indicator, Fig. 1 illustrates in gcaphic form the problem
with such an approach. If one were dealing with only one facility, percent
increase in st excretion would be a valid expression of stress, However,

when different facilities ar> invelved it is apparent that compartSén of incre-
ments does not fairly represent the difference In stress levels. For example,
the mean level of excretion of st by ATCS's during work at Los Angeles (LAX)
Terminal Radar Approach Control (TRACON) did mot even come up to the mean level of
resting excvetion of adrenocorticorteroids of ATCS's at O'Hare ATCT.

By using the product of the adjusted resting and working excretion levels
one can assign appropriate importatc oth values. ese products have been
referred to as individual indices of stress, de ignated as cgt, Ce, and Cne-
The average of the three individual indices is the composite stress index, Cy.

The steps used in computing C, are as follows: .

(Computed for each SI#)

The second problem was related to the baseline_(resting or sleep period) }

believing that the baseline values for all aATCS's would show little variability. ;
In fact, baseline values varied widely from facility to facility. This wide ‘


s

Saket!

ope

soe nal vise Sine e fos mona mpd

nature of the facility, had no dramatic impact on the psychological states of
controllers. Thus, it is clearly inappropriate from the psychological perspec
tive to describe ATC work, as is commonly done in the popular press*, as an
unugually stresaful occupation. Popularized. accounts of controller stress deal
with the exceptional rather than the typical controller or facility. Further, »
such accounta tend to assume that physiological and psychological changes asso-
ciated with simple workload effects are undesirable and invariably have long-te.m
negative consequences. That assumption is highly questionable, particularly tr.
view of the expressed preference of ATCS's for heavy as opposed to light work~
loads (24).

* See Ref. 15 for references to three such popular prese articles.

47



TABLE XXVI. ‘Pathology and Individual Stress
Indices for Vacious ATC Facilities

ss

ap = Level of significance of

#eNS = Not significant

Facility Category Cet BK Ce BY Coe R*
Houston
Intercontinental
re Tower
Normal 1.01 0.40 0.59
| Gastrointestinal 1.77 + 0.96 + 0.57 +
: Cardiovascular 1.77 + 0.96 + 0.57 +
| Neuropsychiatric 0.00 + 0.00 + 0,00 +
\ ‘
4 ha Oakland TRACON
i i a . .
\ booke Normal 0.37 0.85 0.48
i Bet Gastrointestinal 0.48 + 0.41. + 0.30 +
j oo Cardiovascular 0.00 + 0.00 + 9.00 +
F Neuropsychiatric 0.00 + 0.00 f¢ 0.60 +
iN :
bs Los Angeles -
Pook: TRACON
ioe .
a 7
be Normal 0.63 0.38 0.79
an Gastrointestinal 0.00 + 0.00 + 06.00 +
. 4 Cardiovascular 0.00 + 0.00 + 0.00 +
Neuropsychiatric 0.0G + 0.00 + 0.00 *

difference between normals and diseased

+ = Number of cases insufficient for statistical treatment

i
:



pee ; ve ;

14. Welton, c. Ey Re G. Smith, J. M. MeKenzie,” Ss. M. Hoffman, and J. T.
“oSaldivats| Stress in Air Traffic Controllers: Effects of ARTS~III, FAA .
Office of Aviation Medicine Report. No. FAA-AM-76-13, 1976,

Melton, C. E., R. C- ‘Perdonner?’ Low-Density ‘Tou Wicks, and J. T. Saldivar:
Stress in Air Traffic Tontroiieio. “~aoensity Towers and Fright “gervin’*
Stations, FAA Office of Aviation Medicine Report No. FAAMAlir//=20, sos

Also, Aviat. Space Environ. Med., 49:724-728, 1978.

Melton, C: E.: Three Reports Relevant -to Stress in Aviation Personnel. III.
The Relationship Between. Stress-Related Metabolites and Disqualifying Path-
ology in Air Traffic Control Personnel, FAA Office of Aviation Medicine
Report No. FAA~AM-78+5, 1978.

Melton, C. E., J. Ms McKenzie, J. T. Saldivar, and S. M. Wicks: Experi-
mental Attempts to Evoke a Differential Response to Different Stressors,
FAA Office of Aviation Medicine Report No. FAA~AN-78718, 1978,

Helton, Cc. E. TEM MeKenzie, SoM. Wicks, and I T. Baldivar: “Stress in
Air Traffic Controllers: A Restudy of 32 Controllers 5 to 9 Years Later, ~
LOFAA Office of Aviation Medicine Report No. FAA~AM~78-40, 1978. a

“Norymberski, J. K., R. D. Stubbs, and H. F. West: Assessment of Adreno~
“ eortieal Activity by Assay of 17-Ketogenic Steroids in Urine, Lancet,
1276-1281, 1953.0 ; 7 ern

Rochester, §. Ie: Takeott ar Mid Century. Federal Aviation Policy in the
Eisenhower Years 1953-1951. Introduction by N. A. Komons, U.S. Department
of Transportation, Federal Aviation Administration, Washington, D.C., 1976.

Rose, R. Ms, C. Ds Jenkins, and M.W, Hurst: Air Traffic Controller-Health
Change Study, FAA Office of Aviation Medicine Report, No. FAA-AH-78-39, 1978.

Saldivar, J. T., S. M. Hoffman, and C. E. Melton: Sleep in Air Traffic
Controllers, FAA Office of Aviation Medicine Report No. FAA-AM-77-5, 1977.

Schuller, E.: Die Normalaussch:icung der 17-Ketogenen Steroide, Acta

Endocrinol., 21:281-288, 1956.

Smith, R. C.: Stress, Anxiety, avd the Air Traffic Control Specialist:
Some Conclusions From a Decade of desearch, FAA Office of Aviation Medicine
Report No. FAA-AM-80-14, 1980.

. Streng, On: Eine Volkerkarte. Eine Graphische Darstellung der bisherigen
Tsoagglutinationsresultate, Acta Soc. Med. Fenn. Duodecim, 8:1-17, 1927.

¢ Thorn, G. W., D. Jenkins, J. C. Laidlaw, F. C. Goetz, J. F. Dingham,

° W. Ee Avons, 'D. Hy P, Streeten, and B. H. MeCracken} Pharmacologic .
“"" Aspects of Adrenocortical Steroids and ACTH in Man,” New Engl. ‘3. Med. % ;

* 248:323-337, 1953. ene f

4,0. S. Gowcmpeenm PRINT OFFICE 1982 394-727/0K2



wees Nb

TABLE XXIV.
Categories Among Regions and Facilities

Gastro~ Cardio=
Region Facility intestinal vascular
Southern
Opa Locka Tower ti) 0
Miawi ARTCC 3 2
Atlanta ARTCC a i
3 9
Southwest
Houston Inter-
continental Tower 1 1
Fort Worth ARTCC 1 2
2 2
Central
O'Hare Tower (1968) . 4 1
Western
Los Angeles TRACON 0 0
>» akland TRACON 1 o
1 0

Distribution of the Three Major Disease

Neuro~
psychiatric

12

& lo

foo

lo



to cgr (Table XII and Figs. 5-8). wy

There were similarities between ORD and IAH (1970) ATCT's as well as
differences. Both ATCT’s were located at air carrier airports; ATCS's at

both facilities were on the "straight-5" shift-rotation pattern; ATCS's at
both towers worked cab and radar positions. The two facilities differed mainly
in regard to traffic load. ORD commonly had 2,000 operations/d; IAH had about
700 operations/d. The ATC slowdown of 1968 was in effect during the period ofe
the study at ORD. Traffic was normal at LAH in July 1970; however, IAH ATCS's
had just concluded a "Sick out" when our study began and disciplinary actions
were being taken against several ATCS's. AH ATCS's showed quantitatively
less total stress than did ORD controllers; qualitatively, however, ATCS's

at the two towers resembled each other. The heavy~duty shifts at both towers
were associated with elevated excretion of SIH's, reflecting arousal commen-
surate with the workload. Comparisons of ORD and IAH ATCS's are shown in
Tables IX, X, and X1.

Opa Locka Airport (OPF) in surburban Miami, Florida, is an extremely
busy generat aviation airport. The ATCT is a nonradar facility open 16 h/d.
At the time of our study OPF ATCT ranked 10th in the nation in annual number
of operations. Fourteen ATCS's were each monitored on the day shift (0800-
1600) (12). .

rae

OPF ATCS's showed a- pronounced sympatho-adrenomedullary response to
the heavy workload. RT was significantly related to ce and Cg. Workload was
related to cne with weak significance (p < 0.05) and not significantly related

Studies. of ATCS response to.ATCT work were completed with observations
at two low-density. towers in Fayetteville, Arkansas (FYV), and Roswell, New
Mexico (ROW) (15), ROW ATCT ranked 275th (ca. 93,000 operations/yr) and FYV
ranked 404th (ca. 40,000 operations/yr) nationally; at the time of these |
studies there were 424 active U.S. ATCT's.

Arousal, as evidenced by rest-to-work increments in all three urinary
SIH's, was evident in ROW and FYV ATCS's. However, the levels of SIH's in ut
urine were quantitatively less than at ORD, OPF, and IAH (Figs. 2-and 9). i

Epinephrine excretion is also linearly related to annual traffic
count. In Fig. 9, e excretion is graphed against annual traffic count at FYV,
ROW, TAH, OPF, and ORD. Traffic count at ORD has been adjusted to reflect the
fact that a controller at ORD did not handle the entire traffic load. ORD
operated as "two" airports with separate ground controllers and local control- t
lers for the two sides of the airport; thus, only half the traffic load impinged :
ona single controller. When adjustment was made for this arrangement at ORD,
the plotted point fell very near the regression line.

Steroid excretion is not generally related with statistical sig-
nificance to acute ATC workload. Steroid excretion is probably related to
long-term stressors that may or may not be connected with ATC work. It is

“pot uncommon to see a decrease in a controller's st excretion in the at-work

urine specimen, probably reflecting relief through work-related distraction
from some off-the-job stressor.



we

ehift-rotation achedule is not, to say the least, inherently a more disruptive
routine because of sleep loss than is the straight 5, In fact, the average amount
of sleep reported for the workweek by ATCS's on either rotation is somewhat more
than values reported for rotating shift workers in other industries who average
Jess than 6 h of sleep per 24 hb (1).

C. Automation. Manual” radar consists of a display of primary or trans~
ponder returns that give information about azimuth, range, and speed of aircraft.
Altitude: aad aircraft identification are obtained verbally by radio contact with

pilots.. Thus, some degree of uncertainty about aircraft separation attends manual

contral,

(Gomputer-generated radar displays exemplified by the Automated Radar
Terminal System-ILI (ARTS-I11) supplies the air traffic controller with positive
aircraft identification and three-dimensional data regarding location and rate of
movement in tne airspace, thus contributing enormously to safety. ARTS-III also
supposedly eases the workload of controllers by reducing intercontroller coordi-
nation, flight strip activity, radio communication with pilots, and activity
related to radar and radio adjustment: ARTS-IIL differs operationally from the
old radar system in several ways. Conf: .lers do not carry out as much "face to
face" coordination with each other but communicate by telephone. ARTS-III demands
a great deal of keyboard work in use of the computer. The consoles are arranged
in islands equipped. with horizontal cathode ray tubes, and the lighting level is
somewhat higher in the new TRACON facilities than it waa in the old ones. Many
other environmental changes accompanied ARTS-I11: temperature is more closely
controlled, decor is pleasant, and meal facilities are improved. Parking is
clors by, whereas it had been in fairly remote areas at most towers.

. The effect of. ARTS-III on controller stress was estimated from pre~
ARTS-III and pogt-ARTS~III measurements made at LAK and Oakland Bay Area (OAK)
TRACON facilities. (14). When the pre-ARTS-III measurements. were made at Oakland
in August 1972 (OAK~1) and at Los Angeles in November 1972 (LAX-1), the TRACON's
were located in che towers. When the post-ARTS-III studies were carried out in
July 1974 (LAX-2) and November 1974 (OAK-2), the TRACON's were located in builid-
iags separate from the towers. ARTS-III had been operational for about 5 months
at the times of LAX-2 and OAK-2.

Thirteen controllers served as subjects in LAX-1 and 17 in OAK-1. Nine
of the original 13 controllers (69 percent) at LAX and 11 of the original 17
(65 percent) at OAK served as subjects in the post-ARTS-III studies.

The expectation that the benefits of ARTS-III would be realized in
reduced ATCS workload was not entirely fulfilled. Table XX shows a significant
reduction in adrenal steroid excretion by ATCS’s using ARTS~II1, indicating a
reauction in chronic stress attendant on the change to automation. However, cate-
cholatiine excretion was significantly increased to such an extent that total stress
(C,) was greater in the post~ARTS-ITI population than it was in the pre~ARTS-IIT
group (Fig. 11). HR showed no significant pre~ARTS-III to post-ARTS-III change at
either LAX or OAK.

Other Federal Aviation Administration (FAA) studies of the effects of ARTS-
III on centroller workload in the TRACON's at IAH and at Boston Logan Airport have

33



, ‘mnie document iv disseminated under the sponsorship of the
Bepartment of Transportation in the interest of -ioformation

for its content or use thereo!

ae acyhare

t

exchange. The United States Government sesumes no liability Ets

Rereers



TABLE XV. Urine Chemistry

5-Day Vs. 2~2~1 Rotation

TAR ATCT
Rotation .
Pattern Epinephrine  Nocephinephrine 17-KCS 17-KGS, % Baseline

se «1:72 +.0.95 3,654 0.89 1602.79 + 537-70 191.56 + 66.56
Di 2ae Lgl $0.56 3.104 0-81 1244.92 ¥ 293.77 168.69 4 47.19

P NS < 0.01 $< 0.01 N.S.

5 1.47 £0.67 3.98 41,06 1463.00 + 476.35 «179.38 + 80.68
Dz 2 1133 ¥ 0.51 2.954 0.63 1007.93 ¥ 7.7.22. 145.11 4 34.70

P N.S. = 0.05 ‘ N.S.

5 0.27 + 0.10 2.464 1-11 863.4 6.92 100.00
D3 2 0.55 40.21 2.18 $0.44 755.9 2.96 100.00

P << 0.01 NS.

5 1.594 0.80  3.8140.83 © 1532. 94.93 185.40 + 71.98
Dé 2 1137 40.49 3.02 4.0.65 1087.83 4 270.31 «158.17 F 36.26

P N.S. $0.01 o1 WS.

5 0.70 40.42 | 2.76.+0.34 759.84 + 230.46 94,25 + 43.74
re 2 1141 40:56 3-10F 0.81 «1144.92 + 293.77 168.69 F 467-19

P < 0-01 N.S. £0.01 £0.01

5 0.00 0.54 2.92 + 0.60 «1056.90 + 303.07 132,13 + 57.70
7) 2 2133 £0.51 2.95 0.63 1007.93 ¥ 317-22 145.21 & 34.70

P < 0.01 N.S. NS. NS.

5 0.86 40.66 2-49 $0.64 1346.03 + 398.32 169.91 + 66.35
“3 2 0.84 40.71 2.36 © 0.52 755.91 4227.96 150.34 65.47

P NS. 3. < 0,01 NS.

5 0.82 + 0.35 2-85 +.0.45 «1188.88 + 249.34 116.26 + 52.03
MA 2 0193.40.49 2.61 4.0.77 «1087.83 ¥ 270.31 158.17 + 36.26

P NS. N.S N.S. < 0.05
Dl = Day shift specimen #2

D-2 = Day shift specimen #3
De3 = Day shift specimen #1 (night sleep)
D-4 = All #2 and #3 specimens for whole workweek

M-l = Midehift specimen #2

Me2 = Midshift specimen 43

M-3 © Midshift specimen #1 (day sleep)

Me4 = All #2 and #3 specimens for whole workweek

* 5-Day rotattow
‘#*2-2-1 rotation



5)

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TABLE XII. Correlation Coefficients of Cys Cats ©,

and Workload in OPF ATCS's

fe? and ene

Workload
(transmission time)

Set fe __Sne
2 70Ke Bl kee = BBR
- 59K 238
- - 52

264%
+19
o77kk

-55*

elk



Figure 3.

Figure 4.

‘35Q]
© 200]
Eu
190}
0
, ¢ ree
‘ wt ee

Galvanic’ skin response on (A) the 5-day morning shift and (B) the 5-day
evening shift. The daily values are the means of the maximum and minioum
resistances, respectively. (A) shows that the upward trend of ‘mesn maxi-
mum resistance continues over the 5-day period. Such a trend is not

evident for (B).

‘TOTAL PHOBPHOLIPIO AND PHOAPHATIDYL GLYCEROL
‘AG STRESS MOICES BL HUNAN POPULATION

TOTAL PHOSPHOLIPID &
conTROLS }

smmucaTeS
COMBAT FLIGHTS.

ScmTOPHRENICS

exzexoes .

periaie

nant,
COMTROLLERS

mousTon
CONTAOLLERS

oer
PHOSPHATIOYL GLYCEROL,

SeMITOPHREMCS

extewcen
COMBAT FLIONTS

o'MaRe:
CONTROLLERS

Graph of total phospholipid phosphorus and phosphatidyl glycerol. for five.

groups of subjects.

Controllera show a higher titer of all phospholipids

than any of the other groups but their phosphatidyl glycerol level {a more
specific and less variable index than total phospholipid) exceeds only
those of the normal population and simulated combat flight group.

14



\ \, / ‘,
‘TABLE KVI. Plasma Phospholipids : ‘
5-Day Vs. 2-2-1 Rotation ~~
TAH ATCT . ‘
Total Lipid Phosphorus Phosphatidyl Glycerol
Prework 5-Day 2406 + 250.19 (s.d.) 34.23 + 4.16 (#.d.)
2-2-1 2211 + 186.43 27.48 + 3.62
* pe N.S. ‘P< 0.01
: f
ia Postwork 5-Day 2242 + 226.10 (a.d.) 35.16 + 5.44 (8.d.) ‘
\ (Day Shift)
& 2-2-1 | 2222 + 181.60 28.42 + 3.49
x :
be P N.S. P< 0.01
:
bi Postwork 5-Day 2392 + 216.44 (s.d.) 33.19 + 5.35 (s.d.)
: (Midshift) :
uw 2-2-1 2227 + 165.88 29.07 + 3.70 (e.d.) ‘
P B.S. p 0.01
Prework/ 5-Day 14.40. + 51.82 1.47 + 3.50
Postwork (Day Shift)
Differences
2-2-1 26.80 + 41.60 0.80 + 5.37
P : : N.S. : ws.
Prework/ 5-Day -13.92%* + 66.46 1.03 + 4.34
Postwork - 2
Differences 2-2-1 16.00 + 46.63 1.59 + 5.30 :
toe
P N.S. 4S. tpt

* Paired t test
** Prework values higher than postwork values

27

Perce Leama pam tam inna sentngpe nerrmmini eo



. , oy
TABLE II. Comparisons Between Morning Shift and Evening Shift

AVERAGE HEART RATE

Significance Level
Number of ATC Evening Morning +10,..05, .O1, or
in Comparison Activity shift Shift NS (not significant)*

9 Local Control - 101.70 82.51 02
3 Ground Control 100.43 79.93 *
1 Clearance Delivery 90.50 86.00 *
12 Approach Control 90.77 77.23 01
12 Departure Control 84.88 74.83 01

* Data not sufficient to make a statistical test.
** Wilcoxon matched pairs signed rank test.

TABLE Ill. Comparisons* Between Types of Activity During Evening Shift

. Wee

Number of ATC Average Average Significance Level
in Comparison First Activity Heart Rate Second Activity Heart Rate -01,.05, .Ol,or NS***

14 Lecal Control 94.59- Approach Control 89.24 N.S,
14 Local Control 94.37 Departure Control 84.75 01
7 Approach Control 88.55 Departure Control 84.57 05
4 Ground Control 99.20 Local, Control 105.72 biel
2 Ground Control 98.60 Departure Control 95.10 tk
3 Ground Control 97.56 Approach Control 94.23 aK

* Data not sufficient for comparisons among other activities.
&*® Data not sufficient to make a statistical test.
&k# Wtlcoxon matched pairs signed rank test.

TABLE IV.  Comparisons* Between Types of Activity During Morning Shift

Number of ATC Average ‘Average Significance Level
in Comparison First Activity Heart Rate Second Activity Heart Rate 101-05, yor NS#ke

9 Local Control 81.51 . Approach Control 79.51 N.S. :
9 Local Control 81.61 Departure Control 77,89 N.S.
iL Approach Control 75.95 Departure Control 74.16 N.S.
6 Ground Control 79,18 Local Control 83.20 N.S,
6 Grouad Control 78.47 Departure Control - 79.28 RS.
4 Ground Control 76.30 Approach Control 80.42 bail

5 Clearance Delivery 84.02 local Control 83.98 ek

3 Clearance Delivery 83.76 Ground Control 83.90 ae

4 Clearénce Delivery 83,27 Approach Control 78.82 ae

4 Clearance Delivery 85.45 Departure Control 81.22 bial

* Data not sufficient for comparisons among other activities.
*k Data not sufficient to make a statistical test.
*#*k Wilcoxon matched pairs signed rank test.

9



seecpigiar teen hry pe tensegss pega eee one tpn mee rEg JER Meas eee nebo

een gst note

PHYSIOLOGICAL STRESS IN AIR TRAFFIC CONTROLLERS: A REVIEW

INTRODUCTION

The air traffic control (ATC) system that evolved in the period immediately
after Wortd War Il relied on position reports radioed by pilots to air traffic control
specialists (ATCS's). Because of uncertainties inherent in such a system, aircraft
separations in trail were large (60 to 120 miles) by today's standards and system
capacity was correspondingly small. In order to increase production and to meet
schedules, it was a common practice for airline pilots to fly “off airways" in
uncontrolled airspace. As a result, it was predicted that a catastrophic midair
collision would occur, probably over a large city where traffic was concentrated.

Such a collision. did occur, but in one of the nation's most remote locations
“instead of a metropolitan area. On June 30, 1956, a United Air Lines DC-7 and i
‘ta Trans World Air Lines Constellation collided over’ the Grand Canyon, killing all 4
128 persons on board both aircraft. ‘The two airliners were eastbound out of
Los Angeles flying in uncontrolled airspace under visual flight rules at the
time of the accident. The tragic occurrence was a watershed event and served a
to heighten. the government's apprehension about inadequacies of ATC; it also H
caused acceleration of plans for modernization of the airspace system. As Komons
defined the situation in the fifties regarding air traffic control and airway
F's. development, ". . . public policy had fail-d to keep pace with the relentless
“, | march of a runaway aviation technology" (20).

i
t

Thé Grand Canyon crash also aroused unprecedented public concern about the
“crowded. sky." “Books and articles fed public fears about air safety in general
and midair collisions in particular (7). The press hotly attacked the (then)
Civil Aeronautics Authority and Congress. ATC felt the refJected heat.

al With the advent of jet airliners in the late fifties, questions became increas~
ingly urgent about the adequacy of the ATC system to provide safe separation of
afroraft flying at higher altitudes and at ever-greater speeds. Controllers, feel-
ing intense pressure, complained of task overload and excessive responsibility;

the word "stress" began to be associated more and more with ATC.

Nowhere were these complaints more strident than at O'Hare International
Airport in Chicago, I}linois. O'Hare is unique among airports in its rapid rise
to prominence. In less than 20 years the site of this airport changed from farm-
land into the world's busiest air terminal.+ In 1942 the government acquired land
west of Chicago where it built a wartime runway and aircraft assembly plant oper~
ated by Douglas Aircraft Company, facilities that were declared surplus in 1946.
The city of Chicago promptly bought the site plus some adjacent land for a major
new airport to replace Chicago Municipal Airport (Midway), the city's only air
carrier airport and, then, the busiest in the world. However, Midway'a runways
could not be lengthened to accommodate heavy jets and soon became obsolete; O'Hare
then became Chicago's primary airport. Originally, the airport was known as
Orchard Place Airport; a reminder of its beginnings survives in its three-letter
identifier, ORD (2). +By 1961 O’Nare supplanted Midway as the busiest airport in
the wort.



Table XIII shows, where data are sufficient for statistical testing, that
there are ro significant differences during day work between HR's on the two, shift~
rotation patterns for the various work positions. Table XIV shows only one point
of statistically significant difference between midshift positions on the two rota~
tions: approach control radar. Most of the midshift data in Table XIV are insuf-
ficient for statistical comparison because of the fact that only one controller was
in the cab und one in the radar rcom. When the different positions are considered
separately, data for each of them become scanty.

Within the group on the 2-2-1 rotation there are no points of statistically
significant difference in HR's between work positions.

There were no significant differences in urinary e excretion by the two
groups during day work (Table Xv). A significantly elevated excretion of e occurred
during nocturnal sleep by the group ‘on the Q-t~1 rotation; however, & excretion over
an entire week of day work (straight 5) was slightly, but insignificantly, higher
than e excretion of a 5-d week on the 2-2-1 rotation.

When the midshifts were similarly compared, the excretion of e was sig-
nificantly elevated in the 2-2-1 group, except during day sleep when the two groups'
e excretion was equal.

Norepinephrine excretioh was significantly greater during day work on the
straight-5 rotation than on the 2-2+1 rotation, There was no significant difference
in ne excretion during nocturnal sleep on the two rotation patterns.

There were no significant differences in ne excretion by controllers on
the midshifts of the two rotation patterna. Likewise, ne excretion did not differ
“significantly during day sleep on the two rotation patterns. .

17-KGS excretion was significantly higher during the first half of the
midshift on the 2-2-1 rotation than it was during the comparable period on the S-d
rotation. That trend was reversed, however, during day sleep wen st excretion
was significantly elevated in the straight-5 group. When the st data were expressed
as percent of the baseline (night sleep Specimen D-3), adrenocortical -respon~
Siveness was seen to be significantly higher in the 2-2-1 group during the first
half of the midshift and for the whole week that it was on the midshift in the
straight-5 group. Day work was characterized by significantly elevated st excre-
tion by the straight-5 group. The difference between the groups was not seen,
however, during nocturnal sleep. When a week of day work on the straight-5 rota~
tion was compared to day/evening work on the 2-2-1 (Specimen D-4), it was apparent.
that the straight-5 rotation was significantly more stressful than was the 2-2-1
rotation. Adrenocortical responsiveness (percent baseline) was not significantly
different in the two groups.

Table XVI shows that there are no points of statistically significant
difference between the two work schedules as far as total plasma’ phospholipids
are concerned. However, the two shift-rotation patterns can be differentiated
significantly on the basis of phosphat idyiglycerol levels in the controllers'
plasma specimens, with the higher Value occurring in connection with both the day
shift and midshift of the straight-5 rotation. When the change in phospholipid
levels over the workweeks (postwork minus prework levels) on the two rotation pat-
terns were compared, there were no points of significant difference in either
total phospholipid or phosphatidylglycerol levels.

24



no ne AAA NR ETT RE IOP

ern mc eng

EPINEPHRINE (xg /100me CREATININE)

Figure 9.

s
°

isd
2

0.3.

7 2s 4 8 OUT
ANNUAL TRAFFIC COURT. X 10%

Graph of annual traffic count (in millions of
operations) vs. mean urinary excretion levels
of epincphrine of controllers at the various
facilities. Crosses represent on-duty excre~
tion, levels of epinephrine; circles represent
corresponding resting levels (ORD represented
at actual traffic courit and adjusted value
(+) as. described in text).

2



LIST OF FIGURES

Page ;
i
‘Figure 1, Relationship between baseline (night sleep specimen) and 7 {
response (8-hour pooled work specimen) at the various _
facilities. \
. td
Figure 2. Stress at various ATC facilities represented on Streng 7 bo
diagrams.
Figure 3. Galvanic skin response on (A) the 5-day morning shift 14
and (B) the 5-day evening shift, f
Graph of total phospholipid phospliorus and phosphatidyl 14 j j
glycerol for five Broups of subjects. | . 4
5. Relationship between cy and workload. 19
6. Relationship between che and workload. " 19 !
7. ‘Relationship between C, and workload. . 20 i
| Figere 8.- Relationship between cg, and workload. J 20 |
Figure 9. Graph of anual traffic count (in millions of operations) 2 :
vs., mean urinary excretion levels of epinephrine. . 1
Figure 10. Graphic representation of a week on the 2-2-1 and 5-day 23° :
rotations. :
Figure 11. Streng triangles showing the increase in total stress in 35
OAK-2 and LAX-2.
Figure 12. Diagrammatic representation 6f stress in noncontrollers 40.
and active controllers.
\ .
Accession For
WTIS GRAgT 7
DIIC 718
a

| Distributions '
Availability Codes

‘Avall andjer ~4
Dist | Spectaa

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it



bad satel a re ” Sa FRA Ae Rit
: . Technical Report. Documentation Po

Tr Repet No. To Caverament Aecowsion Ne. T Recipient's Coreleg No.

FAA~AN-82-17
TTins ona Sebiiile To Repent Dore

A 198.
PHYSIOLOGICAL STRESS, IN ALR TRAFFIC CONTROLLERS ; < bac ans o Cele
A REVIEW . Perlorming Orgen zation
FT. Foctarming Organiagrion Repert Na.

I hatha

Cc. E. Melton
9, Performing Orgonisotion Name and Address 10.” Work Univ Np. (TRAIS)

FAA Civil Aeromedical Institute
P.O. Box 25082
Oklahoma City, Oklahoma 73125

Ti. Conwect o Grent No.

3. Type of Report ond Period Covered

12. Sponsoring Agency Nowe ond Address

Office of Aviation Medicine OAM Report
Federal Aviation Administration :
800 Independence Avenue, S.W. Ta" Sponsering Agency Code

Washington, D.C... 20591

TS. Supplementary Notes

Cy -
“ ten years of research on physiological stress in air traffic control specialists

(aTCS's) is reviewed. Data were derived from 20 tasks involving the experimental
variables of workload, shift-rotation patterns, and automation, Field studies

were terried vut at Air Traffic Control Towers at Chicago O"Hsre international
Airport, Houston. Intercontinental (two studies), Opa Locka (Florida), Roswell
(New Mexico), and Fayetteville (Arkansas); at Air Route Traffic Control Centers
at Miant, Atlanta, and Fort Worth; and at Flight Service Stations at Oklahoma

_ City, Roswell, and Fayetteville... Laboratory studies at the Civil Aeromedical
Institute consisted of a survey of the quantity and. quality of sleep in working
ATCS's, a restudy of ATCS's several years after the first study to appraise
stress change, and experimental attempts to evoke a differential response to
two different qualities of stress. Stress was distinctly related to imposed

* gorkload as well aa to working conditions. Differences in stress levels in
ATCS's on different shift-rotation patterns were minimal. ‘Automation gave rise
to increased total stress accounted for by an increased workload incident to
the changeover period from manual to computerized control techniques. A stress
index was developed to facilitate comparison of physiological stress at the
different air traffic control (ATC) facilities and among ATCS's. Anxiety level
measurements vary minimally from facility to facility indicating little impact
of ATC work on the psychological state of ATCS's. These and other measures show
that it fs clearly inappropriate to describe ATC work, as is commonly done in
the popular press, as. being unusually stressful. ~

F. Key Words TE. Diewibutidn Siagorent
Air Traffic Controllers, Stress, Document is aveilable to the public chrough}
Workload, Automation, Shift Work, the National Technical Information Service.

Physiological Monitoring, Stress Index | Springfield, Virginia 22161

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LIST OF TABLES (Cont 'd.)

Page.
TABLE XXI. Number of Subjects and Directions of Change in Urine 38
Biochemistry From the First. Study to the Second Study
TABLE XXII. Stress tndicea for Noncontrollers and Active Controllers: 39
Comparison of First aud Second Studies 4
TABLE XXIII. Distribution of Diagnoses Among Three Major Disease 42 1
Categories 4
{
TABLE XXIV. Distribution of the Three Major Disease Categories Among 43 Hl
Regions and Facilities
TABLE XXV. Pathology and Grouped Stress Indices for the Entire Aa
Subject Population
TABLE XXVi. ‘Pathology and Individual Stress Indices for Various ATC : 45 ‘
é Facilities .
TABLE XXVII. Comparison of Excretion Values and Heart Rates for Pong 47
and Treadmill Tasks
“TABLE XXVIII. Statistical Significance of Rest-To-Work Differences for 48 °

the Various Measurements

iv ; ; i



TABLE IX. Urinary Excretion Products Expressed
as Percent of Baseline Values

ORD VS. IAH*
Shift Ept | __Norept,
Day ~ 1st 1/2 “1.04 N.S.#* 0.31 N.S.
Day ~ 2nd 1/2 1.85 N.S. 2.43 < .05
Mid ~ Ist 1/2 4.20 < .01 1.84 N.S.
Mid - 2nd 1/2 4.56 < .01 5.15 < .01
Mid - Postwork 2.42 < .05 3.53 < 01

of t-values, followed by level of significance.

Average Heart Rate

* Mann-Whitney U Test

16

forticosteroid
1.39 NLS.
2.40 < .05
0.16 N.S.
1.30 N.S.
1.05 N.S.

**t test of a difference between two sample means. The chart is a list

***Negative numbers mean that ORD values are lower. than TAH values.

TABLE X.. Comparisons Between oRD and IAH Heart Rates

Activity ORD Tan Significance Level*
— eee =.
Midshift (0200 to 0600) © 72 77 N.S.
Day Shift
(2000 to 1400 ORD)
vs. (1700 to 2100 IAH) 83 90 05
Midshift
CAB Position 78 81
Radar Position 75 78 ~
Supervisor Position 76 76 Te
**Prework 80 86
Day Shift :
CAB Position 81 95. +002
Radar Position 84 87 N.S.
Supervisor Position 86 90 N.S.
**Prework 84 95 01

** One Minute heart rate determination at the time of instrumentation.



me AA | me
ov4

UNCLASSIFIED :

is 7

‘Technical
Report —

distributed by

DEFENSE LOGISTICS AGENCY

Cameron Station « Alexandria, Virginia 22314

UNCLASSIFIED


erm

TABLE XXII, Stress Indices for Noncontrollers and Active
Controllers: Comparison of First and Second Studies ©

Type of Work, Stress, Index-=Mean Values -
Second Study First Study Second Study. Change P<

ACTIVE CONTROLLER

Cot 0.84 0.33 -0.51 0,001
fe 0.53 0.68 40.15 0.05
cne 0.70 0.69 0.01 ns
Cg 0.69 0.57 -0.12 |.” 0.05
NONCONTROLLER
Cat - 0.78 0.19 0.59 0,001
ee 0.48 0.47 -0.01 NS

cne 0.73 054 0.19 NS

Cy 0.66 0.40 0.28 0.05



Evoke a Differential Response
to Different Stressors

TABLE I. Stodies Related to Stress in ATCS's

Date of

Facility (Identifier) Study
O'Hare. ATCT. (ORD) 1968
Houston Intercontinental 1976
ATCT (TAH)

Houston Intercontinental 1971
ATCT (IAH)

Opa Locka ATCT (OPF) 1972
Miami ARTCC (MIA) 1972
Bay Area Approach Control 1972
ATCT (OAK)

‘Los Angeles Approach Con-rol 1972
ATCT (LAX)

Atlanta ARTCC (ATL) 1973
Fort Worth ARTCC (FTW) 1973
Oakland TRACON (OAK) 1974
Los Angeles TRACON (LAX) 1974
The Relationship Between 1975
Stress-Related Metabolites

and Disqualifying Pathology

in Air Traffic Control

Personne?

Oklahoma City FSS (OKC) 1976
Fayetteville FSS (FYV) 1976
Fayetteville ATCT (FYY) 1976
Roswell FSS (ROW) 1977
Roswell ATCT (ROW). 1977
Sleep in Air Traffic 1977
Controllers

Stress in Air Traffic 1978.
Controllers: A Restudy

of 32 Controllers. 5 to 9

Years Later

Experimental Attempts to 1978

Ne
EC

Main Variable Reference
Workload * 49
Workload 10
Shift Schedule ll
Type of Work-Workload 12
Type of Work-Workload 12
Preautomation 16
Preautomation 4
Shift Scheduse 13
Shift Schedule 13
Postautomatton (ARTS II) 14
Postautomation ‘ARTS. 111) ae)
Stress and Medical Conditions 16
Type of Work-Workload 1s
Type of Work-Workload 15
Workload 15
Type of Work-Workload 15
Workload 15
Survey of Sleep Related 22
to Shift, Work

Stress Progression 18

Stressor-Specific Responses.



O'Hare was a new airport as far as terminal facilities were concerned, but

the air traffic control tower (ATCT) and the equipment in it Were obsolete.
Equipment failures were frequent and the view of taxiways from the tower cal

inadequate.

ib was

Problems related to inadequate: staffing, obsolete equipment, heavy workload,
and associated stress continued to grow at O'Hare. In 1968, the Civil Aeromedical
Institute (CAMI) was requested by the Air Traffic Service through the Federal Air
Surgeon to carry out studies at O'Hare ATCT to identify and quantitate sources of
physiological stress. ‘The research task was assigned to the Stress Physiology
Research Unit of the Aviation Physiology Laboratory in CAMI's Aeromedical Research
Branch. ‘Twenty-one subsequent field studies at other facilities and two laboratory
studies were carried out ovér the next 10 years in an effort to characterize and
provide a genetal concept of stress in ATCS's (Table 1). This review is a summary
of those studies, most of which have been previously published.

METHODS

Streas was appraised by a battery of tests, the composition of which changed
somewhat over the course of the studies as redundant, unrewarding, and impractical
teste were dropped. Generally, the test battery consisted of physiological and
biochemical measurements. In the study at O'Hare (9), physiological measurements
taken were ambulatory electrocardiogram (ECG), galvanic skin response (GSR), blood
pressure, and body temperature. Biochemical measurements were made of fibrinogen

and phospholipids in blood and, in collaboration with the USAF School of Aerospace
Medicine at Brooks Air Force Base, Texas, of urinary 17-0H corticosteroids (17-0HCS) ,
epinephrine (e), norepinephrine (ne), sodium, phosphorus, potassium, urea, and
creatinine (er). *In later studies urine analyses were done at CAMI. Urinary sodium,
phosphorus, potassium, and urea were dropped from the battery of tests and measurement
of 17+0HCS was changed to measurement of 17-ketogenic steroids (st), the precursors
of 17-OHCS. All blood measurements were dropped because venipuncture had an adverse
effect on ATCS participation aid because analysis for serum phospholipids, originally
done collaboratively at the Naval Air Development Center, Johnsville, Warminster,
“Pennsylvania, could not be done at CAML or done reliably on contract within budgetary
constraints. Measurements of metallic ions and urea were dropped because they were
judged not to contribute significantly to estimates of stress. The GSR was dropped
because. its measurement interfered with ATCS's activities.

Subjecta were ail volunteers at- the results of these studies are subject to the
bias so created. However, there was no obvious difference in attitudes or condition
of volunteers in one facility from subjects in any other facility. Some ATCS's did
not volunteer because their scheduled shifts did not meet experimental design erd~
teria. Others had conflicts with ‘scheduled annual leave or training; still others
were on medication (e.g., steroids, vitamins, antibiotics) that would have interfered
with the biochemical tests on urine. Only a few ATCS's refused to participate on

principle.

Subjects reported 30 min prior to regular worktime for preshift testing and
ECG electrode hookup, Overtime pay was provided as an incentive for participation.
Bach subject was instructed to void and discard urine on retiring the night hefore

testing and to collect all urine voided from then rhrough arising time, thus collect~

ing all urine formed during the sleep period. Tisy were similarly instructed to void

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OF ARTO ME AT OAKLAND AMD LOS AWSELED. tRACONE,

bs

cy
OAK (72) OAK (74)
: > aso ove
tax (72) bax (74)
oso O76

Figure 11, Streng triangles showing: the increase
in total stress in OAK-2 and LAX-2.
See: Fig. 1 legend for explanation.

35



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D Straight 6-day rotation '= Gay shift back an to mid-anitt
TB 8 hour worn pert

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Figure 10. Graphic represent2“‘on of a week on the 2-2-1
and 5-day rotations. The weeks shown begin on
Monday; however, a controller's workweek may
start on any day and his weekend will neces~ \
sarily be days other than Saturday and Sunday. 7

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First STUDY SECOND sTuDY
Se te
NON-CONTROLLERE
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Figure 12. Diagranmatic representation of stress in
noncontrollers. and active controllers.
Gomparison of first and second studies.

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40

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: B. Shift Rotation Patterns and Sleep. With any activity that requires

a 24-h coverage 7 d/wk, the pattern of rotation of watches is of concern. Time
and attendance requirements usually conatrain employees to work 8 h/d for 5
consecutive days, complicating the scheduling of the work force.

In ATC two besic. work shift rotation Patterns have evolved, the
"straight 5" and the "2-z~:." On the “straight-5" shift-rotation rattern-an
: ATCS worke two 5-d weeks on tne day shift (usually 0800-1600), two 5-d weeks
‘ on an evening shift (usually 1600-2400) and one 5-d week on the midshift (0000=
0800). A 2-d time-off period comes at the end of each 5-d workweek. Of course,
shifts may start and end or any day of the week.

The 2-2-1 shift-rotation pattern calls for the ATCS to work a different
shift each day of the 5-d workweek. Typically, an ATCS would work from 1600 to
2400 on day 1, 1400 to 2200 on day 2, 0800-1600 on day 3, 0700-1500 on day 4,
and 0000-0800 on day 5. Thus, the 2-2-1 pattern involves compression of 40 h
of work into an 88-h period allowing 80 h off duty between workweeks.. On the
straight 5, 40 h of work is spread over 104 h, 96 h, or 112 h, depending on
shift change combinations. Over five workweeks (four intervening off-duty
periods) encompassing the full straight-5 s:ift rotation, an ATCS on the 2-2-1
i gets. a total of 320 h “weekend time," whereas an ATCS on the straight-5 gets a

total of 240 h “weekend time"'—~a difference of 80h. These Patterns are dia>
Bramed in Fig. 10.

In 1970, LAH ATCT was on the Straight-5 shift pattern. ATCS's at IAK
worked a week of evenings, then a week of days, another week of evenings, another
week of days, then a week of midshifts. This was not the work pattern preferred
by most ATCS’s at IAH and considerable labor-management tension was evident as a
result. In 1971 the facility returned to the 2-2-1 pattern, thus affording us an

opportunity to study essentially the same group of ATCS's under both shifc-rotation
Patterns (11).

While the ATCS's liked the 2-2~1 shift pattern, management felt that the
“quick turnaround" inherent in the pattern (Fig. 10) did not allow suffictent time
for rest between work periods, thus leading to a potential for increased error
Tate and excessive use af sick leave because of fatigue.

Nineteen controllers volunteered to Participate in the study: 12 were
journeymen, 5 were supervisors, and 2 were trainees; 12 of them had served
as subjects on the previous 1970 Project. The techniques and measurements
employed were the same as those used on the 1970 project. Briefly, the ECG was
} recorded continuously on tape throughout every work period. Urine was collected
by each subject when he arose each morning (Specimen No. 1), during the first 4 h
(Specimen No. 2), and the last 4h (Specimen No. 3) of each shift. Blood specimens
were taken from each subject when he began his workweek. Urine was analyzed for
€, ne, st, and cr. Blood plasma was analyzed for total Phospholipid and phos~
Phatidylglycerol,

Table XIII shows a comparison of HR's of ATCS's between various.work posi-
tions during day/evening work and midshift work on the two shift-rotation patterns.
Statistically significant differences occurred on the midshift with the average HR
being higher on the 2-2-1 rotation,

22

ERR SIptaree cesar ence



TABLE 1.
TABLE Ii.
TABLE III.
TABLE IV.

TABLE. V.

TABLE VI.
TABLE VII.
TABLE VIII.

TABLE IX.

TABLE X.

TABLE XI.

TABLE XII.

TABLE XIII.

TABLE XIV.

TABLE XV.
TABLE XVI.

TABLE XVII.

TABLE XVIII.

TABLE XIX.

TABLE XX.

LIST OF TABLES

Studies Related.to Stress in ATCS's

Comparisons Between Morning Shift and Evening Shift
Comparisons Between Types of Activity During Evening Shift
Comparisons Between Types of Activity During Morning Shife

Comparison of Plasma Phospholipids of. Air Traffic Con-
trollers and a Normal Population

Summary of SIH Excretion-ORD ATCS's
Data Summary-Control Subjects (Biomedical Team)
Nocturnal Wakefulness. Vs. Nocturnal Sleep

Urinary Excretion Products Expressed as Percent of
Baseline Values

Comparisons Between ORD and IAH Heart Rates

Plasma Phospholipids in yM P/Liter
ORD Vs. IAH ATCS's and Controls

Correlation Coefficients of Cg, Cgts Ce, and Cpe
and: Workload in OPF ATCS's

Comparison of Heart Rates at Different Work Positions
5-Day Vs. 2-2-1 Rotations-IAH ATCT

Comparison of Heart Rates During Midshift Work on 5-Day
and 2-2-1 Rotations

Urine Chemistry 5-Day Vs. 2-2+1 Rotation TAH ATCT
Plasma Phospholipids 5-Day Vs. 2-2-1 Rotation TAH ATCT

Between-Group Comparisons of Resting and Working Values
for Urinary Metabolites From ATL and FTW Controllers

Comparison of Hours of Sleep Prior to Work

Comparison of Average Number of Hours Slept: in Connection
With the Various Shifts (and Days Off) on the Two Rotation
Schedules-Survey of ARTCC ATCS*'s .
Comperisons of Levels.of Urinary Stress Metabolites at
Los Angeles (LAX) and Oakland (OAK) TRACON's Before and
After ARTS=I11 Installation

10

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13

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Bjerner, B.,, A- Holm, ‘and A. Swinasent Om Natt-Och Skiftarbete, Statens.
- Of fentliga Urredningar, Stockholm, 1948, p. 51.

City of Chicago publication: O'Hare--Facts About the World's Busiest
Airport, Department of Aviation, Room 11l1-~City Hall, Chicago, IL, 60602,
1977. . : AMS a 2 .

Gray, 8. J., J. A. Benson, H. M. Spiro, and R. W. Reifenstein: Effects
of ACTH and Cortisone Upon. Stomach, Gastroenterology, 19:658-673, 1952.

Hale, H..B:, E..W. Williams, B. N. Smith, and C. E. Melter: Excretion
Patterns of Air Traffic Controllers, Aerosp. Med., 42:127-138, 1970.

Jorgensen, Mv: On the betermination of 17-Ketogenic Steroids in Urine:
Exeretion in Normal Subjects and After the Administration of Corticot-
rophin,. Acta Endocrinol., 26:424-442, 1957. Beh 8

. eve qe osha ce

Kirener, J. B:, As P. Klotz, and W. L. Palmer: Unfavorable Course of
Gastric Ulcer During Administration of ACTH and Cortiaone, Gastroenterology,
20:27-29, 1952. ee a fetid ese Ay * “

“Knight, C. and %. Ss Knight: Plane Crash, Greenberg, New York, N.Y., 1958.

Maling; H. M. and B. Highman: Exaggerated Ventricular Arrhythmias and ’
Myocardial Fatty Changes After Large Doses cf Norepinephrine and Epinephrine
in the Unanesthetized Dog, Am. J. Physiol., 194:590-596, 1958.

Melton, C. Es, J. Ms McKenzie, B. D. Polis, G. 2. Funkhouser, and P. F.
Iampietro: Physiological Responses in Air Traffic Control Personnel:
O'Hare Tower, FAA Office of Aviation’ Medicine Report No. FAA-AM-71-2, 1971.

Melton, C. E., J. M. McKenzie, B. D. Polis, M. Hoffman, and J. T. Saldivar,
Jr.: Physiological Responses in Air Traffic Control Persotnel: Houston
Intercontinental Tower, FAA Office of Aviation Medicine Report No. FAA~
AM-73-21, 1973. . geen heh nea ey

Melton, C. E., J. .M. McKenzie, R. C. Smith, B. D. Polis, E. A. Higgins,
S. M, Hoffman, G. E. Funkhouser, and J. T. Saldivar: Physiological, Bio~
chemical, and Psychological Responses in Air Traffic Control Personnel:
Comparison of the 5-Day and 2-2-1 Shift Rotation Patterns, FAA Office of
Aviation Medicine Report No. FAA~AM-73~22,: 1973. t

Melton,. C. B., J. Ms McKenzie, J.T. ‘Saldivar; Jr., and'S. M. Hoffman:
Comparison of Opa Locka Tower With Other ATC. Facilities by Means of a
, FAA Office. of, A Medicine,Report, No.

“FAA-AM-74-11, 1974.

: : Be :
Melton, C. B., Re C. Smith, J. Ms McKenafe, J.T. Saldiver, S. M. Hoffra,
and P. R. Fowler: Stress in Air Traffic Controllers: Comparison of Two
Air Route Traffic Control Centers’ on Different Shift Rotation Patterns,
FAA Office of Aviation Medicine Report No. FAA~AM-75-7, 1975.
: os . ‘



less prior to work than they did prior to day work on the 5-d rotation; however,
the one midshift included in the 2~2-1 schedule: substantially lowered the average

amount of sleep because most ATCS's took only @ short nap prior to that single
midshift (Table XVIII).

In a sense, every day on the 2-2-1 schedule fs a quick turnaround day.
ATcS's on the 2-2+1 shift pattern never have 16 h off duty between watches. At
IAH, the amount of sleep taken prior to day 2-was riot significantly different for
the two rotation patterns; on day 3 ATCS's on the straight~5 pattern slept an aver-
age of 57 min more than ATCS's. on the 2-2-1, prior to day 4 the group on the
straight-5 rotation slept 1 h and 11 min longer, and prior to day 5. the control-
lere on the straight-5 rotation slept 4 h and 40 min longer. On-a whole week basis,
when IAH controllers were doing day work on the straight-5 rotation, they slept
an average of 1 h and 36 min longer per night than they did a year later on the
2-2-1 rotation. However, when the single midshift is not included in the compar-
ison, on the 2-2~1 rotation they slept an average of 18 min more than they did the
first 4d of the straight-5 rotation. When a week of work on the 2-2-1 rotation
is compared with a week of midshifts, it develops that the 2-2-1 group slept an
average of 1.h and 2 min more per night than they did on five straight midshifts.

In order to examine further questions regarding the amount of sleep.
obtained in conrection with the 5-d and 2-2-1 shift schedules, a study was carried
out by a questionnaire sent to ‘ATCS's in 35 ARTCC’s in the contiguous 48 states (22).

This survey was conducted with the cooperation of the National Headquarters
Office of the Professional Air Traffic Controllers Organization (PATCO). Letters
requesting volunteers to participate for 5 weeks in the study were sent to the
ARTCC’s by-PATCO's Director of Labor Relations. Sleep logs were then distributed
by PATCO local officials, to controller-volunteers. Completed sleep logs were.
returned to PATCO headquarters for forwarding to CAMI for analysis; thus, complete
anonymity of volunteers was insured.

One hundred and eiglity-five completed questicnnaires were returned.
Thirty-two of the respondent controllers worked the 2-2-1 rotation schedule, and
132 worked the straight-5 schedule. ‘Twenty-one worked rotation échedules dif-
ferent from the 2-2-1 and straight-5 rotation schedules; data from this. group
were excluded.

On the basis of a 7-d week (including 2 days off), the average amount of
sleep obtained by controllers on the 2-2-1 rotation echedule did not differ sig-
nificantly from that obtained by controllers working the straight-5 rotation
schedule (Table XIX). However, when the 5-d workweek (not including 2 daya off)
was considered, the amount of sleep obtained on the two rotation achedules was
significantly different. On the average, controllers working the straight-5
rotation schedule obtained 18 min more sleep per 24~-h period (p < .01) than did
controllers working the 2-2-1 rotation schedule. Again, the difference was
clearly caused by the small amount of sleep obtained by controllers on the 2-2-1
rotation schedule prior te the one midshift. On both rotation schedules, the
greatest amount of sleep was obtained in association with the evening shift,
while the least amount of sleep was associated with the midshift.

This study, conducted on a more extensive basis than the others preceding
it, generally confirmed the findings of those earlier studies; i.e., the 2-2-1

30



TABLE XVIII. Comparison of Hours of Sleep Prior to Work

Weekly Average

Shift Workday (erived from 411
Rotation participating
Pattern 1 2 3 4 5 subjects)
7304 6:58 6:56 TAL 7:10 6:58
5-Day A 1:03 0:09 0:57 Akh 4240 0:53 i
(Days) ;
p*i< 0.05 N.S. £0.05. £0.05 £0.01. ¢ 0.01 !
j
8:07 6249 5259 6:00 2:30 6:05
2-2-1 A. 2:08 2:15. 0:35 0:11 3:50 0:06
peal N.S: NS. WS. NS. £0.01 N.S.
; : ; H
5-Day 5:59 5234 5:24 5:49 6:20 5:59 i
(Mid) ‘

|

* Significance fevel of differencé between values on day shifts and 2-2-1 rotation.
#* Significance level of difference between values on midshifts and 2-2-1 rotation.

3



eto

“Pong” is an electroni¢ television game based on ping~pong. A “ball” is
automatically and randomly directed to one side of the TV screen. Each of the two
players with a knob on the game console controls a "bat" on one side of the display.
The players attempt to intercept ‘the ball. sith the bat, thus returning the ball to
the opponent. When a player misses the ball, a point is automatically scored for
the opponent. The cumulative scare of each player is displayed after each point.
The first player to score 15 points wins tne game. One of the researchers acted
as opponent for all the subjects; she was art expert at the game and was rarely
defeated.

On arrival at the laboratory, subjects were requested to void urine and
discard it. They then had electrocardiographic electrodes attached to their
chests, were given 250 mL of water to drink, and were asked to rest in the supine
position on a cot for 50 min. At the end of the rest period, subjects collected
a urine specimen and began the first work episode.

The electrocardiogram was recorded on an Avionics Electrocardiocorder
for continuous registration of HR. Urine specimens were collected in a 500-mL
graduate cylinder, the volume was recorded, and aliquots were taken for analysis
of st, e, and ne. Aliquots were kept frozen until analyzed. Urinary stress
“hormone values were expressed a8 total weights of the substances excrete’ ducing

c+ -each 50-min episode.

The results of urine and HR analyses are shown in Tables XXVII and XXVIIT.

There ace ‘no statistically significant differences in excretion levels of urinary
metabolites for corresponding episodes of the two tasks. HR's are significantly
higher for the treadmill than for the Pong task (Table XXVIL). Rest-to-work dif-
ferences show that the increment in e excretion is significantly greater during
the Pong: task than during the treadmill task. Rest-to-work differences in excre-
tion of 17-KGS and ne are-not significant for either task. The rest-to-work
increase in HR is significant for the treadmill but not for the Pong task (Table
XXVIII). ;

As reported in an earlier section, field experiments have shown that the
amount of e excreted is significantly and directly related to traffic count and
to radio transmission time. Field study data have strongly suggested that adrenal
steroid exéretion is related to chronic stressors such as Jabor-management dif=
ficulties and that ne excretion is related to physical activity. This laboratory
experiment strengthens the interpretation that e excretion is related to mental
tasks such as ATC and not to physical tasks and, therefore, is the best single
indicator or response to ATC work per se.

E. Conclusion. It should not be inferred from these within-group studies
that excessive or unusual levels of stress were present in the ATC work force.
Studies of non-ATC populations in which exactly comparable measurements were made
are almost nonexistent. However, Hale et al. compared O'Hare ATCS's (the ATCS's
who showed the greatest stress) with various groups previously studied at the
U.S. Air Force School of Aerospace Medicine. They found that ORD ATCS's did not

, uniformly show greater stress levels than did Air Force aircrews, men undergoing
using an anxiety inventory, showed that psychological measures remained relatively
uniform across facilities and suggested that. air traffic work, no matter what the

“altitude chamber tests, or laboratory scientists off duty at home (4). Smith et al.,



we = 720 oe le

WORKLOAD <hmIN>

- Figure 5. Relationshiy between c, and workload represented
‘by minutes of radio communication time.

“= = 72 ss ss ise

WORKLOAD <MIN>

Figure 6. Relationship between c,, and workload represented
by minutes of radio communication time.



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shown a nét reduction’ in ATCS's activities (14). Similarly, the objective measures
of workload in our studies show. either a net decreage in workload or insignificant
change as a result of ARTS-III. Therefore, the increase in total physiological
stress cannot be attributed to increased traffic. .

Conversations with controllers.and supervisors uniformly indicated that
ARTS-III is a major improvemrt in ATC. No ATCS interviewed would have willingly
returned to the old methods. Howsver, there was also general agreement that 5
months of use is not long enough to develop total familiarity and trust in the
equipment. Controllers at both LAX and OAK stated that a complete evaluation by
controllers would be possible only after a good deal more experience had been gained
in this new work environment.

Thus, the increase in the estimated total stress, entirely accounted for
by increased catecholamine output, may be based on controllers’ attitudes at that
time toward ARTS-III. At the time of these studies, controllers‘ attitudes were
sonewhat ambivalent. Controllers liked the reduction in coordination both with
other facilities and within. the TRACON, they liked the sense of privacy at the
radar islande, and they liked the decor and the illumination Jevel. They did not
like the location of the telephone panel and the inconvenience occasioned by
unfamiliarity of other ATC facilities with new 'TRACON procedures.

. ' whe reduced level of excretion of st, after ARTS-III installation, indi-
cates reduction in chronic stress. The chronic stressor could not be positively
identified but it may have related to improved morale in the new quarters,

enlarged controller responsibility (and thus less direct supervision), and improved
labor-management relations.

D. Other Studies, The idea of “burnout” is deeply embedded in the lore of
ATC. The term means that an ATCS believes that he fs no longer able to perform
his active ATC duties. The reasons are not readily discernible but are related

to an accumulation of stress-related problems. cere trtiehnntnn=- sore willl
phenomenon and pointed out that controllers who showed burnout paradox

demonstrated wore psychological health at the start of tnetr-stuty-than-did those
show deterioration in parallel with burnout. > tt burnout
wai related to anincreased incidence of psychological problems, which they spec~
ulate could have resulted in later problems related to health, and performance (21).

We conducted one study to evaluate relatively long-term changes in a
group of ATCS's who had participated in earlier studies. Career progression,
normal aging, and accumulated experience might cause long-term changes in stress
levels (18).

ATCS's were identified as potential subjects through the FAA's Personnel
Management Information System (PMIS). Their participation was solicited by mail;
insulated mailing cartons for shipment of urine specimens were sent to those who
volunteered to participate. They were all males and their ages rangec from 29
to 50 years. Thirty-two volunteers collected urine specimens as previously de-
scribed, répresenting two successive rest and work periods. Subjects were instructed
to refrigerate the specimens and airmail them to CAMI packed with ice. Specimens
were cold when received at CAMI and were analyzed as described earlier; stress
indices were calculated.

36



3. Kae) Cgyy * gry

4. Cz = Set + Se + Sno

x = Individual values,
n = Number of values
% = Mean of individual values

kK, © Mean of individual resting values

XK, * Mean of individual working values \
Xg = Grand mean

Xgy * Adjusted resting value

Xgy * Adjusted working value

"asta * Individual index for any SIH

Cgc = Individual index for 17-KGS

ihn Se 6 dh ae

€e " Individual index for epinephrine
fn * Individual index for norepinephrine

Cg = Composite stress index

The individual indices were used graphically to produce an equilateral trir
angle, the area of which is proportional to Cs. The use of tnt three e-values
to construct a triangle is based on a theorem stating that the sum of the Lengths
of lines joined at an interior point and perpendicular to the sides of an equi-
lateral triangle is equal to the altitude of the triangle.

The c-valueg are represented as Jines originating ec a potnt and diverging
at angles of 120°; the length of each line is proportional to he value of each
individual index. For simplicity's sake, these lines are called vectors. Lines
constructed at. right angles to the “ree ends of the vectors form an equilateral
triangle, the altitude of which is equal to the sum of the tengths of the vectors
{ege + Ce + Cpe)» Thus, the area of the triangle 1s proportional to Cg, the average
Of Cer, Ce, and Cpe (see Fig. 2, ORD).

The use of these stress indices and the diagram, called the Streng triangle
(25), factlitated comparisons of stress at ATC facilities (15).

;"_ Several variables assumed to contribute to ATCS stresa were represented in
| this series of studies. Among them were workload, shift rotation patte.ns, auto-
imation (ARTS III), and "other factora

In the following section results are sum-
marized according to those. variables.



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RESULTS

therefore, a series of studies was carrie 7 wing different
traffic loads in an attempt to measure physirlogical responses in ATCS's to those
different levels. of workload. The first study was carried out at O'Hare ATCT
where physiological responses to the heavy-duty evening sh: 0) were
compared with responses to the relatively light= 00).
Air operations during the early part of the evening shift commonly were in excess
of 200/h; on the morning shift traffic volume was typically about 25 operations/h
during the first half of the shift, but increased sharply on weekdays near’ the
end of the shift (dawn) as air cargo flights arrived in Chicago, Each ATCS-sub-
ject was monitored throughout a full workweek (5 d) on each shift.

.

When mean HR's on the two shifts were compared, it was evident that work-
load on the evening shift gave rise to significantly higher HR's in local control-
lers (cab) and radar controllers (approach and departure) than did the workload on
the morning shift (Table II). Ground control and clearance delivery work did not
give rise to significantly different HR's on the two shifts (Tables III and IV).

During the busy first half of the evening shift, local control and
approacti control positions caused’ ATCS's HR's to be significantly higher than
were HR's during work on ground or departure controi. On the morning shift such
differences were rot statistically significant.

~The GSR (skin electrical resistance) was also related ta workload, being
significantly lower on the evening shift than on the morning shift (Fig. 3). The
GSR decreases with arousal and increases with relaxation. Increasing relaxation
(perhaps somnolence) is shown by the upward trend of mean maximum resistance over
the workweck on the morning shift. On the evening shift no such trend was present
(Fig. 3).

Blood levels of phospholipids in O'Hare ATCS's were significantly higher
than in a group of controls (laboratory workers), Total phospholipids in O'Hare
ATCS’s exceeded values found in schizophrenics and Navy pilots flying carrier~
based combat missions in Vietnam. Phosphatidylglycerol, reported to be a more
specific stress indicator than is total phospholipids, showed ORD ATCS's to be
stressed significantly more than "normals," but less than combat pilots or schizo~
phrenics (Table V, Fig. 4). :

Results of urine analysis (4) for several substances are shown in Tables VI,
VII, and VIII. Generally, ATC work was associated with sympathoadrenomedullary stim
ulation reflected in elevated catecholamine excretion, Recovery to prework levels
was accomplished during night/morning sleep following the evening shift but was not
complete during day sleep after the morning shift, thus providing evidence of cum-
ulative fatigue over five consecutive midshifts. Adrenocortical hyperactivity was
evident only on the morning shift.

ATCS’s at Houston Intercontinental Airport (IAH) ATCT, a medium density
facility, were studied in 1970 co provide data for comparison with ORD ATCS's (10).



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NOTICE

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June 1982



“At
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Branch of CAMI. “These files were searched and 36 controllers were identified who
had developed pathology after the time of the stress study in which they served
as subjects (16). These controklers showed pathology in one or more of three
groups: gastrointestinal, neuropsychiatric, and cardiovascular (Yable XXIII).

A further breakdown of the three conditions by region and facility is shown in
Table XXIV.

The individual and. composite stress indices for normal controllers (those
without a pathology file) and those with pathologicai conditions are rhown in
Table XXV. The table shows that for the whole population of controllers, those
who developed gastrointestinal pathology had significantly (p < -001) higher Coe
than did their normal counterparts at the time they were studied. The index for
norepinephrine (Cpe) was also elevated significantly (p < 0.05) over the normals
for the cardiovascular pathology group.

When the individual facilities were considered, Cpe was significantly
(p < 0.05) elevated tn the cardiovascular pathology group at MIA ARTCC (Table XXVI).
Norepinephrine is the principal catecholamine liberated by the sympathetic nervous
system and is, therefore, the main regulator of arteriolar resistance. Norepineph~
rine has also been shown to: have pronounced effects in causing arrhythmias and
fatty changes in the hearts of dogs (8). There ere no other points of significant
difference. .

This. study suggests that high levels of urinary adrenal steroids are
related to the presence or later development of gastrointestinal disease, the
most common “stress related" ailment. As shown in Table XXIII, the principal
subcategories of that disease relate to ulceration of the stomach and duodenum.
Ulcers have long been known to be related to high levels of endogenous steroids

(3,6,26).

This study suggested that excretion levels of st and ne may be pre~
dictive of gastrointestinal ulceration, heart disease, and hypertension. However,
‘because of the small number of controllers in each diagnostic category, the sta~
tistics leave much to be desired. These findings are, therefore, guarded.

‘The physiological response to real-life stressors, a$ determined by a
battery of measurements, is difficult to interpret. Invariably, a mixture of
stressors is involved, some related to the work situation, others to personal
matters. The response is similarly mixed and not always clearly related to known
stressors. Interpretations of the real-life stress response would be substan~
tially improved if physiological and biochemical responses to “pure” stressors
could be defined. The following experiment was carried out with the goal of pro-
viding such data (17).

Ten healthy paid men (not ATCS's) ranging in age from 19 to 26. years
(average 21.9 years) served as subjects in the experiment. Fach subject was
challenged with two tasks; one was purely physical with no competitive element,
(treadmill), the other was a competitive task that required minimal physical
activity ("Pong"). Order of presentation of the task was balanced. In each
task, subjects were required to work in 50-min episodes. In the 10 min follow~
ing each work eptsode, urine collections were made, rest was allowed, and water
was imbibed to replace urinary loss. This schedule for each task was maintained
for 3h. The treadmill was set at 3 miles per hour with no grade.

41

cat
?



TABLE XIII. Comparison of Heart Rates at 4 “
Different Work Positions .
5-Day Vs. 2-2-1 Rotations-IAH ATCT

Average Heart Rate
5-Day Z-2-1
Work Position Rotation. Rotation peek
Midshift
Radar 73 81 < 0.01
Cab 76 83 < 0.02
Supervisor 76 80 *
Prework 78 83 N.S. :
All positions 76 81 £0.01 wooed
: L
s~
Daywork
Radar . 81 81 N.S.
Cab 81 : 83 N.S.
Supervisor 85 81 ak
Prework 81 83 . N.S.
All positions 81 81. - N.S.
‘4® Data insufficient for statistical test. .
#ke Wilcoxon matched signed rank test.
TABLE XIV. Comparison of Heart Rates During Midshift
Work on 5Day and 2-2-1 Rotations
Average Heart Rate
" 5-Day 2-2-1
Work Position Rotation Rotations pre
Approach control radar 73 81 $0.02
Departure control radar 15 81 iad
Coordinator radar - 82 86 wk
Supervisor radar 7 78 *
Local control cab 75 15 ae —
Ground control cab 79 84 Lat : a
Clearance delivery & data 79 84 . N.S.
#* Data not sufficient for etatistical teat.
ke Wilcoxon matched pairs signed rank test. -
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34



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WORKLOAD <MIN>

Figure 7. Relationship between C, and workload represented

by. minutes of radio coumunication time.

taal x
Me
tel
*
”
x
“ TM x
Se?
=
= “
“ .
ako x rn Uncen ToWER
s x
—<- = = = - = as

WORKLOAD <MIN>

Figure 8. Relationship between cy, and workload represented

by minutes of radio communication time.
20

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\.

- and discard urine just before entering on duty and then to collect in one vessel
(or more if necessary) all urine formed during the work pericd. Normally, sub-
jects collected the last specimen just before they went off duty. Urin2 that
represented the rest ‘nd work periods was thus collected daily. Collections were
made into quart plastic bottles containing an excess of dry boric acid as a
Preservative. Specimens were frozen on receipt from the ATCS‘'s and kept frozen
until thawed for analysis at CANI. Values for urinary hormones were expressed
as the creatiniae-based ratio (w/w) because of uncertainties regarding collec
tion times and volumes (10).

The ECG was recorded on 0.25-in magnetic tape by battery-operated electro-
cardiographs carried in shoulder—slung pouches. The recorder speed was 0.125
in/s and recorders woulu operate reliably for 12 Wi on one battery. ECG tapes
were played back at a speed of 7.5 in/s, thus giving a 60:1 cime advantage when
the taped data were reduced. The tape playback system was coupled to a digital
counter and printer set to count for 1 6 and print the count on Paper; 1s of
Playback was equal to 1 min of recording time. With this system, ECC's recorded
: continuously throughout an 8-h shift could be reduced in 8 min to a list of 1-min
“heart rates (HR's).

A. total of 402 ATCS's served as subjects in those studies.

"Of the variables studied, workload was undoubtedly the most important.

Se ee at count is a good measure of total facility
Fa » DUE Ts not evenly distributed as to quantity or quality among all con-
trollers, Traff‘c count is useful for comparing total workload at different fac~

ilities or for comparing the workload of a given position (e.g., local controi) at
different facilities and was so used in these studies.

Radio time (RT) is defined as the accumulated time that an ATCS spends in
radio contatt with pilots. .The reasoning behind the selection of RT as a measure
of workload is that ATC 1s being carried out only when information relevant to a
flight is being received or transmitted. This definition is a narrow one and
does not take into consideration the time a radar controller spends watching
traffic without verbally communicating with pilots. Furthermore, a radar con-
troller may have traffic on his cathode ray tube (CRT) or "scope" with which he
is not in communication but which, nonetheless, influences his control decisions
and thus affects his workload. In spite of these qualifications, RT was the best
single weasure of workload availeble to us in these studies. RT was obtained by
connecting a seven-channel tape recorder to the output of the facility's recorder
amplifier, thus recording both incoming and outgoing radio transmissions for each
work position. The tapes were played back with the reproducer outputs connected
to voice~actuated relays which, in turn, controlled digital time accumulators,

As ATCS's switched work positions or radio frequencies, tape recorder inputs were
changed to follow from one position te another. Total RT for each controller on
each shift was thus obtained.

nbn catia at ha SNe

4



es - cee Oe .

TABLE XXIII. Distribution of Diagnoses Among

Three Major Disease Categories

Disease :
Categary Diagnosis
Gastrointestinal
Gastric Ulcer
Duodenal Ulcer
Peptic Ulcer
Gastritis
Gall Bladder
Other
Cardiovascular
Myocardial Infarction
Coronary Insufficiency
Hypertension
Angina
Arteriosclerotic Heart Disease
Arrhythr ia
Neuropsychiatric

Anxiety Reaction
Anxiety Depression
“Neuroses"

Cluster Headaches
Depression
Personality Disorder
Schizophrenta
Anxiety Neuroses
Psychosomatic Illness

Percentage

Occurrence

as

nN
PROPER Pore



ae

TABLE “XXV.

Pathology and Grouped Stress Indices.

for the Entire Subject Population

Normal
Gastrointestinal
Cardiovascular

Neuropsychiatric

¢
0.67
1.12
9.94

0.64

£0.01
0.01
NS

NS

0.60

0.61

0.74.

0.82

NS*s

NS

NS;

0.77
0.68
1.25

0.85

NS

£0.05

NS

*P = Level of significance oi difference between normal and
pathological conditions

*4NS = Not significant

Unpaired t~test



ev

. {7 KETOGENIC STEROIDS:
: 300° 7!309
by on,
+ Shen
i 1200 41200
: vse
t 1100 sacra! 100
* Baseline é Work
ae tooo} ME 41000
: su
§ 900] 4 900
i an
: e00 4 600
700 4 700
600] +4600 :
: ove - : free 4
“soo! “4500
400k 4400
sool 300

Figure 1. Relationship between baseline (night sleep specimen) and response
(8-hour. pooled work specimen) at che various facilities. Ordinate
is ug 17-KGS (st) per 100 mg of creatinine.

DA AA

omc ancre
oe te on on on
tan ere van Cro nonce eantras unere
‘ese aver - ‘raacom art
an on rey

DAbABAS

won bertial oes cree revere ervcer enecray
apace rae
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Figure 2. Stress at various ATC facilities represented on Streng diagrams.

7