STRESS IN AIR TRAFFIC CONTROLLERS: COMPARISON OF TWO AIR

ROUTE TRAFFIC CONTROL CENTERS ON DIFFERENT SHIFT
ROTATION PATTERNS

I. Introduction.

On the straight 5-day shift rotation schedule,
the controller works 5 days on the same shift,
has 2 days off, then works 5 days on a different:
shift; 104 hours are required to accomplish a
week’s work. The pattern is repeated until ro-
tation has occurred through all shifts; one rota-
tion cycle requires 5 to 6 weeks, The main
feature of the 5-day shift pattern is a 16-hour
off-duty period between 8-hour work periods.

On the standard 2-2-1 rotation pattern (2
evenings, 2 days, 1 midshift), the controller
works a different shift every day and, by so
doing, compresses his 5-day workweek into 88
hours. For example, a controller on the 2-2-1
schedule works 1600-2400 on day 1, 1400-2200
on day 2, 0800-1600 on day 3, 0700-1500 on day
4, and 2400-0800 on day 5. He is then off duty
from 0800 on his fifth day until 1600 on the first
day of his next workweek. Thus, a controller
on the 2-2-1 schedule has 80 hours off duty be-
tween workweeks as compared to 72 hours that
a controller on the straight 5-day schedule has
off-duty. The extended off-duty period is ob-
tained by shift compression, which, in turn, oc-
curs by reduction of off-duty time between work
periods—the so-called “quick turnaround.” On
the schedule outlined above, a controller is off
duty for 14 hours between his first and second
days, 10 hours between his second and third
days, 11 hours between his third and fourth
days, and 9 hours between his fourth and fifth
days. On the 2-2-1 schedule the lone midshift
is always the last work period in the week and
is always followed by scheduled days off. Nor-
mally, controllers are scheduled to work 8 hours
with the meal break being included in the 8
hours.

FAA management usually looks with disfavor
on the 2-2-1 rotation pattern because controllers

usually cannot take 8 hours of rest between shifts
when the turnaround time is only 9 to 14 hours.
Management feels that fatigue brought on by
the 2-9-1 schedule contributes to excessive use
of sick leave and possibly to compensable claims.

Dille compared medical records from two air
youte traffic control centers (ARTCC), one on
the 2-2-1 shift rotation schedule and the other
on the straight 5-day schedule. Because of mul-
tiple factors in the data, he could not conclusively
relate incidence of disease at the facilities to
shift schedule; however, the disability retirement
rate was four times as high and pending dis-
ability claims were twice as numerous at the
5-day facility.

A study carried out at Houston Interconti-
nental Tower (IAH) showed that there was
little difference between the two shift rotation
patterns as far as physiological or psychological
stress was concerned, and such difference as
existed indicated that the 2-2-1 pattern was less
stressful than the 5-day schedule.?

Because the results of the IAH study did not
confirm that the 5-day schedule was physiologi-
cally less stressful than the 2-2-1 pattern, further
study was strongly indicated. Two ARTCC’s
were chosen as project sites because centers have
a larger number of controllers than do towers
and therefore could be expected to yield a larger
number of volunteer subjects.

The Atlanta ARTCC (ATL) was selected to
represent. the 5-day rotation pattern and the
Fort Worth ARTCC (FTW), to represent the
2-2-1 pattern. These two centers have several
common characteristics, such as size, climate, and
relationship to nearby cities.

II. Methods.

Twenty-three male controllers at ATI (aver-
age age: 37 years) and 29 at FTW (average



Tate 8 Average Workload (Transmission Time) at
ATL and FTW
ADL. EBL
Day Shift 32.9 38.1
Evening Shift 30.5 28.4
Midshift 4.9 9.0

were no significant overall differences between
groups on either the A-trait or A-state measures.
There was some slight (although statistically
insignificant) variance in anxiety levels accord-
ing to shifts. The evening shifts had the highest
scores for both groups; however, the day shifts
were lowest for the 5-day sequence and the mid-
shifts were lowest for the 2-2-1 schedule.

As in previous studies,? it was consistently
found in this study that significant differences
existed between the A-State Scale scores obtained
before and those obtained after each work shift.
In each case, anxiety levels were reported to in-
crease as a function of work.

In comparison to other normative groups for
the STAI, the air traffic controllers scored rela-
tively low on both the A-trait and A-state meas-
ures. In comparison with the norms for college
students (of the various normative groups in-
cluding hospital patients, college freshmen, high
school students, psychiatric patients, college un-
dergraduates had the lowest overall anxiety
level), it was found that the average A-trait
score for both shift groups considered together
is equivalent to the 27th percentile; that is, it

Taste 9. Average Amount of Reported Sleep (hr) Prior to Hach Shift at ATL and FTW

ATL
Number of Weekly
Subjects Shift Day Number Average
1 2 3 4 5
7 Day 6.97 7.27 6.78 6.83 6.56 6.88
7 Evening 9.19 7.42 7.84 8.49 7.67 8.12
9 Mid 5.93 7.11 6.68 6.04 7.04 6.56
FTW
Number of Weekly
Observations Shift Day Number Average
1 2 3 4 5
AL * 8.38 7.75 7.23 6.31 2.98 6.53
12 hail 8.89 7.58 6.55 6.31 5.71 7.01
6 wk 8.13 6.25 7.13 6.78 7.42 7.14

*Midshift on 5th work day
**Day shift on 5th work day
“Day shifts only


each controller once at the beginning and again
at the end of the study. The first administration
of the A-Trait Scale occurred before a control-
ler’s initial shift and the second, at the comple-
tion of the final shift considered for each con-
troller. 7

Center workload was recorded at each facility
as total radio transmission time on seven sectors
identified by line supervisors as fairly represent-
ing total traffic. Workload was normalized by
expressing transmission time as percentage of
total recording (shift) time.

IIL. Results.

Table 1 shows the comparison of resting and
working values for st, e, and ne at ATL and

FTW. There were no significant differences in
e excretion during sleep between ‘he two facili-
ties. At each of the facilities, nowever, st, e,
and ne excretion was greatest during day sleep
following midshift work. Excretion of st and
ne by ATL controllers during sleep (day or
night) was significantly greater than the output
of those stress indicators by FTW controllers.

Table 1 shows that e excretion during work
was not significantly different on any shift at
ATL and FTW. Excretion of ne was signifi-
cantly higher at ATL than at FTW on all three
shifts. However, st excretion on the day and
evening shifts was significantly higher at ATL
than at FTW; the difference in st excretion dur-
ing the midshift work was insignificant.

‘Taste 2, Within-Group Comparisons of Urinary Metabolites at ATL and FTW (Avg. ,g/100 mg creatinine)

ATL
Midshift Day shift Evening Shift
Re wee P R Ww B R w P
st 987.3 469.1 N.S. 533.2 1193.1 < 0.01 831.8 877.3 N.S.
e 0.5 0.8 N.S, 0.4 1.2 < 0.01 0.4 Ll < 0.05
ne 4.5 3.9 N.S. 2.6 4,5 $0.01 3.6 5.4 < 0.05
FTW
st 429.7 332.3 N.S. 284.2 700.9 < 0.01 362.8 499.9 = 0.01
e 0.7 0.8 N.S. 0.5 1.6 $0.01 0.5 1.3 $0.01
ne 1.3 1.3 NS. 1.2 2.2 = 0.01 1.2 5.4 < 0.01

* Resting values
%* Working values

In Table 2, the data in Table 1 have been re-
organized to show differences in resting and
working values at ATL and FTW. At neither
facility were the differences significant for st, e,
or ne on the midshift. In fact, st and ne excre-
tion declined slightly during midshift work
from the day sleep level. The differences be-
tween resting and working values for all three
urinary constituents were statistically significant
and greatest in magnitude on the day shift, with
the exception that the increment in excretion of
ne was greatest at FTW on the evening shift.
Steroid excretion at ATL was not significantly

increased during the evening shift over the base-
line level; all other values increased on the eve-
ning shift at both facilities and the increases
were statistically significant.

‘An earlier publication from this laboratory
presented a biochemical stress index (Cs) com-
puted from the average of the products of nor-
malized baseline and working values of st, e, and
ne (Cet; Ce, and Cae) Table 3 shows ATC fa-
cilities studied from 1968 to the present time
ranked according to C, computed for all work
shifts. ATL yanks third in the list and FTW
ranks ninth.



Tasre 1. Between-Group Comparisons of Resting and Working Values for Urinary Metabolites From ATL and
FTW Controllers
Resting Values
st & ne
Ds* Re Neer Ds NS Ns Ds NS Ns
ATL 987.3 533.2 831.8 0.52 0.35 0.38 4.47 2.56 3.55
FIW 429.7 284.2 362.8 0.73 0.52 0.53 1.28 1.15 1.16
Pp < 0.05 $0.01 $0.01 N.S. N.S. N.S. < 0.01 < 0.01 $0.01
Working Values
Shift Shift shift
Mid Day Evening _Mid Day Evening Mia _Day_ Evening
ATL 469.1 1193.1 877.3 0.84 1.17 1.1L 3.88 4.45 5.44
FTW 332.3 700.9 499.9 0.78 1,55 1.25 1.28 2.19 2.08
p N.S < 0.01 <0.01 N.S. N.S. N.S. $0.01 $0.01 $0.01

*DS = Day sleep, midshift work
#*NS = Night sleep, day shift work
HENS = Night sleep, evening shift work

age: 35 years) volunteered to serve as subjects.
Twenty-three of the FTW controllers were on
the 2-2-1 rotation schedule and six were on the
5-day pattern. Data on the 23 FTW controllers
on the standard 2-2-1 pattern are compared with
that of ATL controllers on the 5-day rotation
pattern. Data on the six FTW controllers on
the 5-day shift patterns are presented separately.

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

At FTW, 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 FTW controllers worked
all three shifts (day, midshift, and evening) and
13 worked days and evenings only.

Subjects at both facilities collected urine on
arising from their sleep periods. For those on

the day and evening shifts, these specimens were
composed of urine formed during night sleep;
for those on the midshift, the specimens were
composed of urine formed during day sleep.
The night sleep specimen was used as the base-
line specimen in all estimates of stress.

Urine was analyzed, as previously reported,*
for 17-ketogenic steroids (st), epinephrine (e),
and norepinephrine (ne). These urinary me-
tabolites are reported as micrograms per 100 mg
of urinary creatinine (ug/100 mg cr). The three
metabolites are referenced to creatinine because
of uncertainties about urine volumes and times
of collection inherent in specimens collected out-
side controlled laboratory conditions.

The State-Trait Anxiety Inventory (STAI)*
was used to assess psychological aspects of con-
troller stress. Each controller completed the
A-State Scale (a measure of moment-to-moment
levels of anxiety) of the STAI immediately be-
fore and after each work period. In addition,
the A-Trait Scale (a measure of anxiety prone-
ness or general anxiety level) was answered by


TABLE 5. Cat, Ce, ANd Cae for Each Shift at ATL and FTW

Day Shift Evening Shift Midshift
st Se “ne Sst Se “ne “st °e ne
ATL 0.70 0.33 0.91 0.81 0.34 1.72 -- -- --
FIW 0.29 0.72 0.22 0.22 0.57 0.22 0.12 0.27 0.13
the lengths of lines (see ORD, Fig. 1) originat- — Tasre 6. Internal Comparison of 5-Day and 2-2-1 Ro-
ing at a common point and diverging at angles tations at FTW—Day- Shift Only
of 120°. Lines perpendicular to the ends of the
vectors form an equilateral triangle, the altitude Reating Values
of which is equal to the sum of the lengths of the a a as
diverging lines. One-third of the altitude of the = *#” whe 0.59 0.97
triangle is equal to C,; thus, the area (or size) 2-21 284.2 0.50 1,20
of the triangle, while not equal to, is propor- NS. xs. MS.
tional to C,. It is apparent from these triangles
that total stress (C,) at ATL exceeds total stress working Values
at FTW and that c,. is the largest individual a = a
value at ATL while c, is the largest value at *** 525.6 1,29 134
FTW. 2-2-1 700.9 1,60 2.20
At FTW a comparison by means of the stress? Bes. NS. NS.
index showed that the six controllers on the « « es <
5-day rotation did not differ significantly from a ~ = =~
the 23 controllers on the 2-2-1 rotation (Table oaay on ost on ot
6). aed 0.23, 0.62 0.23 0.36
Ns. Rs. nS. ns

RELATIONSHIP OF Cet, Cg, Cpe REPRESENTED
ON THE STRENG TRIANGLE

Ax A A A

Che
ORD OPF ATL MIA
Cs= 1.05 0.84 0.82 0.76
1AH (70) 1AH (‘71 OAK LAX FTW
0.74 0.68 0.60 0.60 0.34

Fioure 1. Relationship between ¢st, Ce, and Cae repre-
sented on the Streng triangle. The size of the
triangle is proportional to Cs.

The findings from the STAI indicate that
anxiety levels were essentially equal for control-
lers on both rotation schedules (Table 7). There

‘Tanrg 7. Mean A-Trait and A-State Raw Scores for
Air Traffic Controllers Under Two Shift Rotation

Schedules
Rotation Schedule
scale shite Tine 2201
ATratt - anon 28.9
A-State Day Before 26.1 32.2
After pyeEy 36.6
Evening Before 32.5 35.2
After 375 36.6
Midnite Before 30.4 28.9
After 33.4 34.0
overall 31.9 32.9



Technical Report Documentation Page

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.
FAA-AM-75-7

4. Title and Subtitle 5. Report Date

STRESS IN AIR TRAFFIC CONTROLLERS: COMPARISON OF

TWO AIR ROUTE TRAFFIC CONTROL CENTERS ON DIFFERENT S-Povloming Orgonivation Code

SHIFT ROTATION PATTERNS

[8. Performing Organization Report No.

7. Author's) C, E, Melton, R. C. Smith, J. M. McKenzie,
J. T. Saldivar, S. M. Hoffmann, and P. R. Fowler

9. Performing Organization Nome and Address 10. Work Unit No. (TRAIS)
FAA Civil Aeromedical Institute
P. O. Box 25082 TY. Contract or Grant No.

Oklahoma City, Oklahoma 73125

13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address
Office of Aviation Medicine
Federal Aviation Administration OAM Report
800 Independence Avenue, S.W. . 14. Sponsoring Agency Code
Washington, D.C. 20591

TS. Supplementary Notes

Work was performed under Task AM-C-74-PHY-72

16. Abstract

Stress in 23 air traffic controllers (ATCS) at Atlanta Air Route Traffic Control
Center (ATL) on the straight 5-day shift rotation schedule was compared with stress
in 23 ATCS's on the 2-2-1 shift rotation schedule at Fort Worth Air Route Traffic
Control Center (FTW). Stress in six other FTW ATCS's on the 5-day schedule was
compared to stress in their 23 cohorts on the 2-2-1 schedule. Stress estimates
were made from urinary levels of 17-ketogenic steroids (st), epinephrine (e),

and norepinephrine (ne). There were no statistically significant between-group
differences in e excretion. Levels of st and ne were significantly higher

for ATL ATCS's under all conditions. Ranking by composite stress index (C,) of ATC
facilities showed that ATL ranked third and FTW, ninth. When C, was calculated for
shifts, FIW ranked last in stressfulness on all shifts. ATL ranked fifth on the
day shift and second on the evening shift. There were no significant differences
in excretion of st, e, and ne between the FIW ATCS's on the 2-2-1 schedule and
those on the straight 5-day schedule. Mean scores for neither anxiety trait
(A-trait) nor anxiety state (A-state) were significantly different at FIW and ATL
and the scores of controllers at both facilities were low compared to those of
other normative groups. It is concluded that physiological stress at ATL is
significantly greater than at FIW. The difference probably cannot be accounted for
by the shift schedules, since stress in the group at FIW on the 5-day schedule does
not differ significantly from stress in their cohorts on the 2-2-1 schedule.

17. Key Words 18. Distribution Statement
Air traffic control, Stress index, Document is available to the public through
Shift work the National Technical Information Service,

Springfield, Virginia 22151

19. Security Classif. (of this report) 2. Security Classif. (of this page) 21. No. of Pages 22. Price
$3.00 PC
Unclassified Unclassified .95 MF

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized



to bed 1 hour 42 minutes earlier when working
the day shift than they did when working the
evening shift, but they slept 2 hours 59 minutes
later the morning after the evening shift than
they did the morning after the day shift.
Figure 2 is a line graph of the average amount
of sleep day-by-day at ATL and FTW. It is

Sleep Comparison Between ATL and FTW

100
90 fF
80Fr
TOF
a. 60F
Wn 50
wae SOF ATLANTA n
n~ 40Pr @—® doy shift \
O—A Evening Shift N
30Pr O—O Midshift i)
20F FT. WORTH
Lor O--D 2, 2, | Rotation
} + 4 + 4
\ 2 3 4 5
DAY
Ficure 2, Line graph on the average amounts of sleep

taken by controllers on the 2-2-1 and 5-day shift
rotation patterns.

clear from inspection that the amount of daily
sleep by controllers was more consistent through-
out the workweek at ATL than at FTW. At
FTW there was a definite decline in the amount
of daily sleep throughout the workweek. The
six controllers at FTW on the 5-day schedule
show a sleep pattern resembling the patterns at
ATL.

IV. Discussion.

Physiological stress among FTW controllers
is measurably less than among ATL controllers.
Since the FTW ARTCC was on the 2-2-1 rota-
tion schedule, it is clear that, in and of itself,
there is no physiological support for the convic-
tion that the 2-2-1 schedule is more taxing than
the 5-day schedule to the individual controller.
However, it would be equally unjustifiable to
consider the 2-2-1 schedule necessarily—or al-

ways—superior to the 5-day schedule. The
differences probably are minimal, as suggested
by the comparisons between the six controllers
on the 5-day pattern and the 23 controllers on
the 2-2-1 schedule at FTW; no significant dif-
ferences were shown on the variables considered.

Apparently, the managerial set against the
2-2-1 rotation is largely rooted in the belief that
controllers on such a schedule get insufficient
rest. between shifts. When the entire workweek
is considered, ATL controllers averaged about a
half hour more sleep per night than did FTW
controllers. The difference in favor of ATL is
entirely accounted for, however, by FTW con-
trollers’ practice of taking only a short nap be-
fore their single midshift. When only the first
4 days of the week are considered (ie., the mid-
shift is not considered), FTW controllers slept
about a half hour longer than did ATL control-
lers. It is doubtful that the difference in stress
is explainable in terms of the relative amounts
of sleep taken by controllers at the two facilities.

It would be misleading to consider the mid-
shift as a very-low-stress shift, primarily because
the stress of midshift work is inseparable from
the stress of day sleep. The data show that ex-
cretion of st, e, and ne is greatest at both facili-
ties during day sleep. The elevated excretion of
catecholamines during day sleep may be partially
explained by circadian effects, though elevated
steroid excretion runs counter to the early morn-
ing circadian maximum.

Steroid and norepinephrine excretion by ATL
controllers during day sleep was greater than
the excretion of those substances by FTW con-
trollers during day sleep. Epinephrine excretion
during day sleep was not significantly different
for the two groups of controllers. It was shown
in another study that e excretion was more
closely related to workload than was the excre-
tion of st and ne* Since workload is at a mini-
mum during the rest period, it is not surprising
to find no difference in e excretion between the
facilities.

Norepinephrine represents sympathetic nervous
system activity. The elevation of ne in the
urine of ATL controllers may be interpreted to
mean that ATL controllers did not relax as well
during day sleep as did FTW controllers. Sig-
nificantly elevated st excretion in ATL control-
Jers during day sleep indicates that they were


Taste 10, Average Bedtime/Arising Time at ATL and FTW

ATL.
Work Day No. 1 2 3 4 5
Shift
Day 23397 a0 23307 6 230, 73397 09 2353 96
Evening 70/915 07107 a5 0130/ on 0541 903 07127 59
Mid 2000/7, 035 0909 / 606 ONT ose 09307, 532 0357 159
FIw
Midshift 5th day 00107 a32 00537 a8 234/65 2310/9 18177, 153
Day shift 5th day 23357 09 01257 58 23547) a 2325) 2348 531
Day shift only 0005/ > 0008/3 0038/ 0018) 2305/

essentially would fall in the lowest quarter of
the college student scores, The overall A-state
score obtained before work, 30.9, is at the 33rd
percentile while the corresponding score after
work, 34.9, falls at the 99th percentile on these
norms. These levels are closely comparable to
those obtained at the IAH Tower.

Workload on the three shifts at the two cen-
ters is shown in Table 8. No correlation of
workload with stress in any individuals could be
made because of the way that workload was
recorded. There is a generally positive correla-
tion of facility workload with facility C, at
FTW while the correlation is negative at ATL.
Workloads at the two centers are similar except
that the correlation for the midshift workload
is somewhat higher at FTW than at ATL.

Data were obtained by questionnaire on the
amount of sleep obtained prior to each of the
five work periods. Table 9 shows the average
amount of sleep obtained prior to each day’s
work by controllers at ATL and FTW. At
both facilities controllers slept most in connec-

tion with the evening shift and least prior to
the midshift. Overall, ATL controllers slept
18 minutes more per sleep period than did FTW
controllers. However, when the single midshift
is not considered, FTW controllers slept an av-
erage of 32 minutes more per sleep period than
did ATL controllers on the day shift, 42 minutes
less than ATL controllers on the evening shift,
and 51 minutes more than ATL controllers on
the midshift. When the midshift is considered
in the workweek at FTW, ATL controllers on
five straight midshifts slept an average of only
2 minutes more per sleep period than did their
FTW counterparts.

Bedtimes and arising times are shown in Table
10, and it is apparent that the longer sleep
period associated with the evening shift occurred
because of late morning sleep. Average bedtime
for ATL controllers on the day shift was 2339
while their average bedtime on the evening shift
was 0121. The average arising times, however,
were 0630 at ATL on the day shift and 0929 on
the evening shift. Thus, ATL controllers went



Taste 8. Ranking of ATC Facilities by Stress Index
(C.) Computed for All Work Conditions

O'Hare Tower 1.05
Opa Locka Tower 0.84
Atlanta ARTCC 0.82
Miami ARTCC 0.76
Kouston Intercontinental Tower (1970, 5-day shift) 0.74
Houston Intercontinental Tower (1971, 2-2-1 shift) 0.68
Oakland TRACON (pre-ARTS-I11) 0.60
Los Angeles TRACON (pre-ARTS-I11) 0.60
Fort Worth ARTCC 0.34

*AlL Cy values calculated by using night sleep as baseline.
‘s

Table 4 shows the ranking of C, computed for
the day shift, evening shift, and midshift at
various ATC facilities. ATL and FTW rank
fifth and ninth respectively in total stress (C,)
on the day shift. ATL ranks second and FTW
ranks fourth on the evening shift. FTW ranks
fourth on the midshift; C, could not be calcu-
lated for the midshift at ATL because data

representing night sleep (baseline) were not col-
lected from the seven controllers who worked
the midshift. No midshift work data were col-
lected at Miami ARTCC, Opa Locka Tower,
Oakland TRACON, or Los Angeles TRACON.
No day shift data were collected at O’Hare
Tower. No evening shift data were collected at
IAH Tower (1970), Miami ARTCC, Opa Locka
Tower, Oakland TRACON, or Los Angeles
TRACON. The stress index, which was formu-
lated after these studies were completed, could
not be calculated for the shifts listed above.

Table 5 shows the values for ¢st, Ce, and Cpe at
ATL and FTW for the three shifts. It is ap-
parent that the catecholamines contribute mainly
to the magnitude of C,. It is interesting that
ne is the prime determinant of C, on the day
and evening shifts at ATL whereas c, is the
prime determinant of C, on all three shifts at
FTW.

The relationships of C., cst; Ce) aNd Cpe at the
ATC facilities studied to date are shown on
Streng triangles in Figure 1.67 This triangle is
useful in showing the relationship between three
variables and is based on the theorem that the
sum of the perpendicular distances of any in-
terior point from the sides of an equilateral
triangle is equal to the altitude of the triangle.
The values of cst, Ce, and Cae are represented by

Tape 4. Ranking of ATC Facilities by Stress Index (C,) Calculated for Different Shifts

Day Shift Evening shift Midshift
Facility c, Facility ¢, Facility ¢,

Pouston Intercontinental

Tower (1970, 5-day shift) 0,92 O'Hare Tower 1,09 O*Hare Tower 1,01
Houston Intercontinental

Opa Locka Tower 0.84 Atlanta ARTCC 0.96 Tower (1971, 2-2-1 shift) 0.57

Houston Intercontinental Houston Intercontinental Houston Intercontinental

Tower (1971, 2-2-1 shift) 0.79 Tower (1971, 2-2-1 shift) 0.65 Tower, (1970, 5-day shift) 0.55

Miami ARTCC 0.76 Fort Worth ARTCC 0.34 Fort Worth ARTCC 0.21

Atlanta ARTCC 0.64

Oakland TRACON (pre-ARTS-

111) 0.60

Los Angeles TRACON

(pre-ARTS-IIT) 0.60

Fort Worth ARTCC 0.41






ACKNOWLEDGMENT

We wish to acknowledge our indebtedness to Mr. Al Houck, Chief,
Atlanta ARTCC, and to Mr. C. Otho Reasoner, Chief, Fort Worth ARTCC,
for their support in the conduct of this research. Our deep gratitude goes
to Mr. Wes Bryant, Atlanta ARTCC, and Mr. Sid Hughes, Fort Worth
ARTCC, for their daily help and guidance while we were in their facilities.
Our special thanks go to the 52 controllers who participated as subjects in
these studies and to all the others who offered their help and insights.





experiencing some sort of continuous physiologi-
cal stress, perhaps related to the five straight
midshifts.

It seems reasonably clear that the two shift
schedules are essentially equal in the degree to
which anxiety is aroused. It does appear that
controllers experience somewhat more anxiety
while engaged in work (A-state) than they do
on the average in other settings (as estimated by
the A-Trait Scale) ; however, the extent to which
their anxiety increases as a function of their
work seems well within normal limits. It must
therefore be concluded that (1) controllers as a
group, at least at these two installations, are not
under undue psychological stress, as measured
by the STAI, and (2) the alternating shift
schedules do not have an appreciable effect on
such stress levels.

It is probable that the differences in the stress-
arousing properties of the 2-2-1 and 5-day
schedules, in both a physiological and a psycho-
logical sense, are relatively minimal. The dif-
ferences in physiological stress favoring FTW
were probably due to relatively low levels of
stress at this facility rather than to excessively
high levels of stress at ATL, since the indices
were also low at that location. Certainly, any
negative effect of working under the 2-2-1
schedule was not sufficient to unduly arouse
FTW personnel. It therefore seems appropriate
to conclude that there is little justification, in
the sense of physiological or psychological stress
arousal, for the necessity of choosing one sched-
ule over the other, although if these data are
decisive in such decision making, the choice
would be in the direction of the 2-2-1 schedule.

REFERENCES

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2. Melton, C. E., J. M. McKenzie, R. C. Smith, B. D.
Polis, E. A. Higgins, 8. M. Hoffmann, G. B. Funk-
houser, and J. T. Saldivar, Jr.: Physiological, Bio-
chemical, and Psychological Responses in Air Traffic
Control Personnel: Comparison of the 5-Day and
22-1 Shift Rotation Patterns. FAA Office of Avia-
tion Medicine Report No. FAA-AM~78-22, 1973.

8. Melton, C. B,J. M. McKenzie, B. D. Polis, S. M.

‘Hoffmann, and J. T. Saldivar, Jr.: Physiological

Responses in Air Traffic Control Personnel: Houston

Intercontinental Tower. FAA Office of Aviation

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cs

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. Spielberger, C. D., R. L. Gorsuch, and R. E. Lushene:
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6. Streng, O.: Eine Volkerkarte. ine graphische
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. Streng, O.: Das Isoagglutinationsphanomen yom
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