1. Report No. 2. Government Accession No. 

FAA-AM-77-23 

4. Title and Subtitle 

STRESS IN AIR TRAFFIC PERSONNEL: LOW-DENSITY 

TOWERS AND FLIGHT SERVICE STATIONS 

Technical Report Documentation Page 

3. Recipient's Catalog No. 

5. Report Date 

September 1977 

6. Performing Organization Code 

AAM 

t--;;---;--;--;-;--;:;---;;:;--:;-;;---o;-:----;o;---;;---;o;--..-;-.,.---~~;----;-;--;-;,..--.-----! 8. Performing 0 rgon i zoti on Report No. 

7. Authorls) C. E. Melton, R. C. Smith, J. M. McKenz1.e, 

S, M. Wicks~ and J. T. Saldivar 

9. Performing Orgoni zotion Name and Address 

FAA Civil Aeromedical Institute 

P. 0. Box 25082 

Oklahoma City, Oklahoma 73125 

10. Work Unit No. (TRAIS) 

11. Contract or Grant No. 

r-:-:--:---------:----:-:--:-:-------------------113. Type of Report and Period Covered 

12. Sponsoring Agency Name and Address 

Office of Aviation Medicine 

Federal Aviation 

8·00 Independence 

Washington D.C. 15 .• Supplementary Notes 

Administration 

Avenue, S.W. 

20591 

14. Sponsoring Agency Code 

FAA 

Work was performed under Task AM-C-77-PHY-83. 

16. Abstract 

Stress and anxiety levels were measured l.n 10 a1r traffic control specialists 

(ATCS) at two low-traffic-density towers, Fayetteville (FYV), Arkansas, and 

Roswell (ROW), New Mexico, and 1n 24 flight serv1ce (FS) specialists at Oklahoma 

City (OKC), Oklahoma, Fayetteville, Arkansas, and Roswell, New Mexico, Physiological measurements consisted of heart rate and urine biochemical analysis for 

17-ketogenic steroids, epinephrine, and norepinephrine. 

On-duty arousal in ATCS's and FS specialists was evident both physiologically 

and psychologically; such arousal was within psychologically normal limits and 

was generally low physiologically compared to other a1r traffic control (ATC) 

facilities that have been studied 1n the past, Physiological stress levels at 

these low-density towers and flight service stations were also low compared to 

other ATC facilities that were studied previously. It 1s concluded that it l.S 

inappropriate to describe all air traffic control work, as is commonly done in 

the popular press, as unusually stressful. Such accounts 1.n the popular press 

tend to deal with the exceptional rather than with the typical controller or 

facility. 

17. Key Words 

Stress 

Air Traffic Controllers 

Anxiety 

Workload 

19. Security Classif. (of this report) 

Unclassified 

Form DOT F 1700.7 (8-72) 

18, Distribution Statement 

Document 1s available to the public through 

the National Technical Information Service, 

Springfield, Virginia 22161. 

20. Security Clossif. (of this page) 21. No. of Pages 22. Price 

Unclassified 17 

Reproduction of completed page authorized 

STRESS IN AIR TRAFFIC PERSONNEL: LOW-DENSITY 

TOWERS AND FLIGHT SERVICE STATIONS 

I. Introduction. 

Air traffic control specialists (ATCS) have been extensively studied with regard to the ergonometric, physiological, 

and psychological demands of their profession; however, as 

Kalsbeek (1) has pointed out, there is a strong tendency to 

take measurements only under conditions of overload. This 

practice has contributed to the popular idea that all air 

traffic controllers are under a great deal of stress. Sensationalized pseudoscientific reports have reinforced this 

general concept (2,3,4). 

Most air traffic control towers (ATCT) are not high-density 

facilities. The total number of operations at ATCT's in 1976 

ranged from 718,143 at O'Hare to 10,370 at Deadhorse, Alaska 

(5). More than 50 percent of the total ATCT operations took 

place at 27 percent of the ATCT's. Sixty-two percent of the 

ATCT's had less than 100,000 operations in 1976 (5); thus, 

most are not high-density facilities, and any generalization 

about stress in ATCT's must take ·that fact into account. 

Total operations and national ranking for the facilities in 

the study reported here are shown in Table 1. 

In his presentation of a paper in 1976 (1), Kalsbeek represented stress versus load in ATCT 1 s as theoretically conforming 

to aU-shaped curve (Fig. 1). There are considerably more data 

related to Kalsbeek's zone of overload than there are to the 

zone of underload; yet this condition of low-level activity 

characterizes work on the mid shift at some air traffic control 

(ATC) facilities and virtually all work at others where traffic 

volume is low. 

Eleven studies at eight ATC facilities have been carried 

out in previous years by this laboratory in an attempt to 

provide a general characterization of stress associated with 

ATC work. All these studies have been conducted at high- or 

medium-density facilities. To describe stress in terminal 

ATCS 1 s equitably, however, it is necessary to include representation from ATCT's of various levels of activity. Towers 

at Drake Field in Fayetteville, Arkansas, and Industrial Air 

Center in Roswell 1 New Mexico 1 were selected as sites for the 

present study to provide data from low-density terminal facilities and thus complete the spectrum of levels of tower workload, 

1 
TABLE 1. Total Operations and National Ranking of OKC, 

FYV, and ROW FSS's and ATCT's in 1976 (5) 

Total National 

Facility Operations Ranking 

OKC FSS 425,582* 40** 

FYV FSS 95,490* 226 

ROW FSS 75,028* 256 

ROW ATCT 93,296 275*** 

FYV ATCT 39' 722 404 

* Includes telephone and face-to-face weather briefings 

as well as radio callups. 

** Total U.S. FSS's: 347 

***Total U.S. ATCT's: 424 

2 
~ 

0 

0 

._ 

~ 

> 

0 

~ 

0 

0 

~ 

0 

E 

Figure 1. Theoretical curve relating the stress response to 

load (1). 

3 
In characterizing stress associated with air traffic control, it is also necessary to consider the type of work being 

done. For this reason, it was thought to be essential that 

data from flight service stations (FSS) be included in any 

general description of stress associated with ATC work. 

Accordingly, FSS 1 s at Oklahoma City (OKC), Fayetteville (FYV}, 

and Roswell (ROW) were chosen as study sites. Cost effectiveness and accessibility were the principal factors involved 

in these selections. 

II. Methods. 

Thirty-four ATCS 1 s and flight service (FS) specialists 

ranging in age from 23 to 60 years volunteered to serve as 

subjects in the study (Table 2). There were two female subjects--one FS specialist at ROW and one at OKC, 

All subjects were instrumented for ambulato~y electrocardiography when they reported for duty on the day shift. 

Silver-paste chest electrodes were attached as previously 

described (6); leads from the electrodes were connected to 

an Avioni,cs Model 400 Electrocardiocorder. Continuous electrocardiograms were recorded from each subject throughout the 

day shift. Electrocardiographic tapes were played back on an 

Avionics Electrocardioscanner whose output was fed to a counter 

and printer so that a digital record of 1-minute heart rates 

was produced. 

Urine was collected throughout a 5-day workweek. Two 

pooled specimens/day were collected representing (i) the 8-h 

work day, and (ii} the night sleep period. Collections were 

made into 1-qt screw-capped plastic bottles containing an 

excess of dry boric acid as a preservative. Specimens were 

logged and immediately placed in a freezer, where they were 

kept frozen until thawed for analysis. The specimen consisting 

of urine formed during night sleep was used for resting values, 

Subjects brought this night sleep specimen with them when they 

reported for duty. Urine was analyzed for 17-ketogenic 

steroids (17-KGS), epinephrine, norepinephrine, and creatinine 

as previously described ~). Values are expressed as weight 

per 100 mg creatinine. 

The State-Trait Anxiety Inventory (STAI) (8) was used to 

measure the psychological arousal of the participants. Each 

subject completed the A-State scale of the STAI as a measure 

4 
TABLE 2. Urinary Metabolite Excretion Data ~g/100 mg Creatinine 

17-KGS Epinephrine Norepinephrine 

Facilitr No. Rest Work P* Rest Work p-1: Rest Work P* --

OKC FSS 13 423.10 713.00 0.01 0.56 1.17 0.01 2.29 3.37 0.01 

FYV FSS 8 414."70 608.30 0.01 0.57 1.05 0.01 2.10 2.52 0.05 

V1 ROW FSS 3 500.80 718.5.0 NS 0.67 1.30 NS 3.05 4.55 NS 

FYV ATCT 4 551.70 807.90 NS 0.53 0.86 0.01 1. 97 2.14 NS 

ROW ATCT 6 526.40 829.00 0.05 0.66 1.03 0.05 2.26 2.60 NS 

* Paired t-test 
of current arousal or anxiety level immediately before and 

after each work day. The general propensity of the individuals to experience anxiety, as reflected in their reports 

of typical arousal levels, was measured by the A-Trait scale 

of the STAI just before the initial shift of the study. 

III. Results. 

Heart Rate. Mean heart rates at the several facilities 

are shown in Table 3. The only statistically significant 

change (~ < .01) in heart rate from before-duty to on-duty 

conditions occurred at ROW FSS, where the mean rate decreased 

by 11 beats per minute. 

TABLE 3. Mean Heart Rates at the Several Facilities 

MEAN HEART RATE (bern + SEM) 

Facility Before duty On duty p 

OKC FSS 80 ± 1 82 ± 1 NS 

ROW FSS 98 ± 5 87 ± 2 0.01 

FYV FSS 84 ± 2 80 ± 3 NS 

ROW ATCT 92 ± 4 85 ± 2 NS 

FYV ATCT 79 ± 1 73 ± 4 NS 

Urine Chemistry. Excretion values for the three metabolites under resting and working conditions at the five 

facilities are shown in Table 2. It is evident from these 

data that there are consistent duty-related increases in all 

three urinary excretion products; some of the increases 

achieved statistical significance at OKC and FYV FSS's and 

at FYV and ROW ATCT's. 

6 
A comparison of these facilities with others by means of 

a stress index (9) is shown in Table 4. This ranking by composite stress index (C ) shows that OKC FSS, FYV FSS and ATCT, 

s 

and ROW ATCT are positioned at the low end of the stress 

spectrum. The position of ROW FSS in the ranking must be 

interpreted with the knowledge that only three FS specialists 

participated at that facility and that the relatively high 

C for ROW was caused by the copious excretion of all three 

s 

stress indicators by only one of the subjects. 

The values in Table 4 are shown graphically 

In this diagram, the values of c , c , and c 

st e ne 

in Figure 2. 

are presented 

as vectors. Lines perpendicular to the ends of the vectors 

form an equilateral triangle whose altitude is equal to the 

sum of the vectors; therefore, the area of the triangle is 

proportional to C (the average of c , c , and c ). The 

s st e ne 

area of the triangle thus represents total stress, and the 

relative contributions of effluents from adrenal cortex, 

adrenal medulla, and sympathetic nervous system can be ascertained from the lengths of the internal lines. This diagram 

was first used by Otto Streng to show the relationship of 

three isoagglutinins (10). 

State-Trait Anxiety Inventory. The mean A-Trait scores 

for the two groups of participants differed significantly 

(~ < .OS) with the FSS group showing a tendency toward higher 

scores (Table 5). By using collegiate undergraduate normative 

data, we determined that the mean FSS score falls at the 36th 

percentile, while the mean ATCT score falls at the 14th percentile. In terms of A-Trait data taken from past studies of 

controllers (11,12,13,14), the mean for the FSS group falls 

approximately at the 70th percentile of all previously studied 

controllers, while the mean for the present ATCT group falls 

at the 45th percentile. In other words, these FSS personnel 

score high relative to other controllers in proneness to 

anxiety arousal, while the individuals in the present ATCT 

group have an average level of anxiety proneness for controllers. 

The difference between the two groups on the A-Trait scale 

was also noted in the A-State scale scores (Table 5). Both 

before-shift and after-shift A-State scores were significantly 

(~ < .05) higher for the FSS than for the ATCT group. 

7 
TABLE 4. Comparison of Various ATC Facilities 

by Means of a Stress Index 

Facility G c c c 

s st e rie 

O'Hare ATCT ('68) 1.05 1.41 0.75 0.98 

Opa Locka ATCT ('72) 0.84 0.64 0.74 1.15 

Atlanta ARTCC ('73) 0.82 0.76 0.34 1. 37 

Miami ARTCC ('72) 0.76 0.61 o. 71 0.96 

Los Angeles TRACON ('74) 0.75 0.27 1.10 1.44 

Houston ATCT ('70) 0.74 1.27 0.29 0.65 

Roswell FSS ('76) 0.73 0.40 0.69 1.10 

Oakland TRACON ('74) o. 72 0.23 1.31 0.61 

Houston ATCT ( 1 71) 0.68 0.89 0.62 0.52 

Oakland TRACON ( I 72 ) 0.60 0.62 0.76 0.43 

Los Angeles TRACON (I 72) 0.60 0.66 0.34 0.81 

Roswell ATCT ('76) 0.49 0.45 0.50 0.50 

Oklahoma Citl FSS ('76) 0.47 0.33 0.49 0.59 

Faletteville ATCT ('76) 0.40 0.49 0.36 0.34 

Faxetteville FSS ('76) 0.39 0.28 0.46 0.42 

Fort Worth ARTCC ('73) 0.34 0.22 0.58 0.20 

8 
Cne 

ORO C'68) 

ATCT 

C5= 1.05 

LAX ('74) 

TRACON 

0.75 

OAKC'72) 

TRACON 

0.60 

IAH ('70) 

ATCT 

0.74 

LAX !'72) 

TRACON 

0.60 

OPF c'72) 

ATCT 

0.84 

ROW('76) 

FSS 

0.73 

ATL C'73) 

ARTCC 

0.82 

OAKC'74) 

TRACON 

0.72 

MIA ('72) 

ARTCC 

0.76 

IAHC'71) 

ATCT 

0.68 

ROW C'76) 

ATCT 

0.49 

OKC ('76) 

FSS 

0.47 

FYV !'76) FYV('76) FTWC'73) 

ATCT 

0.40 

FSS 

0.39 

AATCC 

0.34 

Figure 2. Stress at various ATC facilities represented on 

Streng diagrams. 

9 
However, if the A-State scores are adjusted for the difference 

in mean A-Trait scores, the differences in A-State scores 

become statistically negligible. 

In most of the previous studies of psychological arousal 

in air traffic controllers, there has been an increase in 

A-State scores from before to after work shifts (11,12,13). 

In the present study, a like increase was found for both groups 

of subjects (Table 5). For the FSS group, by using college 

undergraduate norms, we found that the means ranged from a 

level equivalent to the 43rd percentile before work to the 

59th percentile after work C£ < .01). The ATCT group showed 

a similar degree of increase, from the 18th percentile to the 

35th percentile (~ < .01). In comparison to data obtained 

from other groups of controllers, the mean FSS scores would 

fall at the 61st and 81st percentiles for before- and 

after-work scores respectively, while the corresponding mean 

ATCT scores would be at the 18th and 44th percentiles. 

TABLE 5. Mean A-Trait and A-State Raw Scores for ATCS's 

at Low-Traffic-Density ATCT's and FSS's 

A-Trait 

A-State Before Work 

A-State After Work 

IV. Discussion. 

ATCT's 

(n = 10) 

28.0 

27.4 

31.4 

FSS's 

(n = 25) 

32.6 

33.4 

37.4 

Taken in the aggregate, urinary and heart rate data 

indicate that work at these FSS's and ATCT's is relatively 

low in stress content. On-duty arousal is evidenced by an 

increase in urinary output of all metabolites, but this 

increase is either less or no greater than that at busier 

facilities. (See Table 6 for rankings of ATC facilities 

according to the extent of biochemical arousal.) 

10 
TABLE 6. Ranking of Facilities in Decreasing Order of On-Duty 

Arousal as Indicated by Urinary Metabolites 

Ranking 17-KGS 

1 FTW ARTCC ( 1 73) 

2 ATL ARTCC ( 1 73) 

3 LAX TRACON ( 1 72) 

4 OAK TRACON ( 1 74) 

5 OPF ATCT ( 1 72) 

6 OAK TRACON ( 1 72) 

7 LAX TRACON ( 1 74) 

8 MIA ARTCC ( 1 72) 

9 IAH ATCT ( 1 70) 

10 OKC FSS ( 1 76) 

11 ROW ATCT ( 1 76) 

12 FYV FSS ( 1 76) 

13 FYV ATCT ( 1 76) 

14 ROW FSS ( 1 76) 

15 IAH ATCT ( 1 71) 

16 ORD ATCT ( 1 68) 

Epinephrine 

IAH ATCT ( 1 70) 

OPF ATCT ( 1 72) 

MIA ARTCC ( 1 72) 

OAK TRACON ( 1 72) 

FTW ARTCC ( 1 73) 

LAX TRACON ( 1 72) 

ATL ARTCC ( 1 73) 

OAK TRACON ( 1 74) 

ORD ATCT ( 1 68) 

LAX TRACON ( 1 74) 

IAH ATCT ( 1 71) 

FYV ATCT ( 1 76) 

OKC FSS ( 1 76) 

ROW FSS ( 1 76) 

FYV FSS ( 1 76) 

ROW ATCT ( 1 76) 

11 

Norepinephrine 

OPF ATCT ( 1 72) 

LAX TRACON ( 1 72) 

MIA ARTCC ( 1 72) 

FTW ARTCC ( 1 73) 

ORD ATCT ( 1 68) 

ATL ARTCC ( 1 73) 

LAX TRACON ( 1 74) 

OAK TRACON ( 1 72) 

IAH ATCT ( 1 70) 

OAK TRACON ( 1 74) 

ROW FSS ( 1 76) 

FYV ATCT ( 1 76) 

OKC FSS ( 1 76) 

IAH ATCT ( I 71 ) 

FYV FSS ( 1 76) 

ROW ATCT ( 1 76) 
Figure 3 is a graph of resting and working levels of 

epinephrine excretion at six ATCT's versus annual traffic 

counts at the times the studies were conducted. The relationship for the working values is significant (R = 0.96) 

with O'Hare being the exception. However, it should be 

pointed out that work at O'Hare was divided, with separate 

cab control positions for the north and south sides of the 

airport; one side of the airport was customarily used for 

departures and the other for arrivals, thus the work was 

about equally divided between the two sides. Two radar 

approach and two departure control positions also reduced 

the traffic load impinging on each controller. If the 

traffic count at O'Hare is halved to reflect the fact that 

only half the traffic load impinged on each controller, then 

the epinephrine excretion value for O'Hare controllers falls 

near the line of best fit for the other ATCT's. Epinephrine 

excretion therefore appears to be the best indicator of 

responsiveness to work involving direct control of aircraft. 

This finding confirms an earlier observation at Opa Locka 

ATCT, where a strong correlation was found between radio 

communication time and epinephrine excretion (9). Resting 

values showed no such relationship. 

As expected from past observations, excretion values for 

norepinephrine and 17-ketogenic steroids are not so clearly 

related to traffic count as is epinephrine excretion. 

Steroid excretion at FYV and ROW ATCT's is lower than at other 

ATCT's that have been studied. Norepinephrine excretion is 

lower at ROW than at other ATCT's, but it is as high at FYV 

as at Opa Locka and O'Hare. These two metabolites are reported 

to reflect chronic stress (steroids) (15) and physical activity 

(norepinephrine) (16) and are, therefore, not as indicative 

of the response to ATC work as is epinephrine. 

Total stress (C ) and duty-related arousal in these FS 

s 

specialists rank near those same measurements for their counterparts in low-density ATCT's. The relationship between total 

operations and epinephrine excretion does not hold, however, 

for FS specialists. This lack of correspondence is perhaps 

due to the fact that FSS work is not concerned with the direct 

control of air traffic. 

The findings from the STAI are generally consistent with 

results obtained from other controller populations in that 

12 
w 

z 

z 

i= 

ct 3.0 w 

a:: 

u 

0> 2.5 E 

0 

0 

" 0> 2.0 

::t.. ORO 

-w 

z 1.5 ( +}.-······-·"·-··· ............... " ............... -·-"""+ 

a:: 

::J: 

Q. 

w 1.0 

z 

a: 

w 

0.5 

0 0 

0 

.I .2 .3 .4 .5 .6 .7 

ANNUAL TRAFFIC COUNT X 10 6 

Figure 3. Graph of annual traffic count (in millions of 

operations) vs. mean urinary excretion levels of 

epinephrine of controllers at the various facilities. 

Crosses represent on-duty excretion levels of 

epinephrine; circles represent corresponding resting 

levels (ORD represented at actual traffic count and 

adjusted value (+) as described in text). 

13 
ATC and FS specialist work has some apparently moderate 

arousing quality (11,12,13). As in the previous studies, 

the absolute level of arousal experienced in undertaking 

this kind of work is entirely within normal limits. 

The significant difference between typical (A-Trait) 

arousal levels of FSS and ATCT personnel follows other data 

(17,18) that indicate that FSS personnel differ from controllers to some noticeable degree on certain characteristics. 

In this case, FS specialists report a tendency to experience 

arousal that is greater than that reported by controllers, 

although again it must be emphasized that the degree of 

sensitivity to the arousal of feelings of anxiety expressed 

by FS specialists is well within normal limits. It seems 

likely, in view of the accumulating evidence, that these 

differences are due to selection factors operating in the a1r 

traffic system. In other words, individuals who work in 

FSS's as opposed to other types of air traffic facilities 

probably do so because certain characteristics distinguish 

them from other air traffic personnel. This study suggests 

that one of these characteristics may be the basic susceptibility of an individual to experience arousal of anxiety. 

The FS specialist typically shows very normal tendencies 1n 

this respect and is high in susceptibility only relative to 

the typically lower susceptibility of controllers. 

The extent to which these data may be generalized to all 

smaller air traffic facilities remains to be determined, because 

there are distinct geographical limits to the present sample. 

However, these data do fit the pattern established by our earlier field studies and provide a perspective from which to 

assess the impact of air traffic work on the physiological 

and psychological status of the controller workforce. There 

is nothing in the present data that suggests unusual reactions 

in either domain. The data from all the air traffic facilities 

indicate that epinephrine is the physiological measure most 

closely associated with traffic count, a finding consistent 

with the report of Patkai (19) that epinephrine excretion is 

related to level of general activation. On the other hand the 

psychological measures remain relatively uniform across facilities and suggest that air traffic work, no matter what the 

nature of the facility, has no dramatic impact on the psychological states of controllers. Thus, it is clearly inappropriate to describe air traffic control work, as is commonly 

14 
done in the popular press (2,3,4), as an unusually stressful 

occupation. Popularized accounts of controller stress deal 

with the exceptional rather than the typical controller or 

facility. Further, such accounts tend to assume that physiological and psychological changes associated with simple 

workload effects are undesirable and invariably have long 

term negative consequences. That assumption is highly 

questionable, particularly in view of the expressed preference of air traffic controllers for heavy as opposed to light 

workloads (18). 

15 
References 

1. Kalsbeek, J. W. H.: Some Aspects of Stress Measurements in 

Air Traffic Control Officers at Schipol Airport. Symposium 

on Stresses of the Air Traffic Control Officer (Latest 

Development), pp. 39-46, University of Manchester, Department 

of Post-Graduate Medical Studies, April 1976. 

2. Collier, B.: In His Own Words an Atlanta Psychiatrist Worries 

Over Air Traffic Controllers Who Crack Under the Strain. An 

Interview With Dr. Merton Berger, PEOPLE, 8:54-58, 1977. 

3. Lehmann, P.: Job Stress: Hidden Hazard, JOB SAFETY AND HEALTH, 

2:4-10, 1974. 

4. Martindale, D.: Sweaty Palms ~n the Control Tower, PSYCHOLOGY 

TODAY, 10:73-75, 1977. 

5. FAA Air Traffic Activity, Calendar Year 1976, U.S. Department 

of Transportation, Federal Aviation Administration, Office 

of Management Systems, Information and Statistics Division. 

6. Saldivar, J. T., Jr.: A Simplified Technique for Rapid Application of Dry ECG Electrodes, AEROSP. MED., 4:456, 1970. 

7. Melton, C. E., J. M. McKenzie, B. D. Polis, S.M. Hoffmann, 

and J. T. Saldivar, Jr.: Physiological Responses in Air T~affic 

Control Personnel: Houston Intercontinental Tower, FAA Office 

of Aviation Medicine Report No. AM-73-21, 1973. 

8. Spielberger, C. D., R. L. Gorsuch, and R. F. Luchene: Manual 

for the State-Trait Anxiety Inventory, Palo Alto, CA, Consulting 

Psychologist Press, 1970. 

9. Melton, C. E., J. M. McKenzie, J. T. Saldivar, and S.M. 

Hoffmann: Comparison of Opa Locka Tower With Other ATC 

Facilities by Means of a Stress Index, FAA Office of Aviation 

Medicine Report No. AM-74-11, 1974. 

10. Streng, 0.: Eine Volkerkarte. Eine Graphische Darstellung der 

bisherigen Isoagglutinationsresultate, ACTA SOC. MED. FENN. 

DUODECIM, 8:1-17, 1927. 

16 
11. Melton, C. E., J. M. McKenzie, R. C. Smith, B. D. Polis, E. 

A. Higgins, S. M. Hoffmann, G. E. Funkhouser, and J. T. 

Saldivar, Jr.: Physiological, Biochemical, 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. AM-73-22, 1973. 

12. Melton, C. E., R. C. Smith, J. M. McKenzie, J. T. Saldivar, 

S. M. Hoffmann, 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 Report No. AM-75-7, 1975. 

13. Smith, R. C., and C. E. Melton: Susceptibility to Anxiety and 

Shift Difficulty as Determinants of State Anxiety in Air 

Traffic Controllers, AEROSP. MED., 45:599-601, 1974. 

14. Melton, C. E., Jr., R. C. Smith, J. M. McKenzie, S.M. Hoffmann, 

and J. T. Saldivar: Stress in Air Traffic Controllers: Effects 

of ARTS-III, FAA Office of Aviation Medicine Report No. AM-76-13, 

1976. 

15. Kagan, A. R., and L. Levi: Health and EnvironmentPsychosocial Stimuli, A Review. Reports from the Laboratory for 

Clinical Stress Research No. 27, December 1971. 

16. Adkins, J. R., T. I. Miller, T. Carter, and J. D. Hardy: The 

Hormonal Mediation of Neurovascular Reflex Adjustments: 

Catecholamine Response to Postural Changes in Man, AMER. J. 

SURG., 27:210, 1961. 

17. Smith, R. C.: Vocational Interests of Air Traffic Control 

Personnel, AEROSP. MED., 46:871-877, 1975. 

18. Smith, R. C.: Job Attitudes of Air Traffic Controllers: A 

Comparison of Three Air Traffic Control Specialties, FAA Office 

of Aviation Medicine Report No. AM-73-2, 1973. 

19. Patkai, P.: Catecholamine Excretion in Pleasant and Unpleasant 

Situations, ACTA PSYCHOLOGICA, 35:352-363, 1971. 

17