: vas not detected: within’ a predetermined tinie
limit, a “conflict alert’. occurred signifying a

conflict. was. detected, either: “by the subject or
following. a “conflict-alert” alarm, the subject had
‘to. decide: whether a ‘conflict existed ‘or -not
(whether" the 2° aircraft were flying directly
"toward’:each other, or. not). For: both’ types of

 etitical ents” in’ the primary ‘task, ‘subjects:

problems. ‘Subjects were always controlling 16
aircraft: ‘when’ one left the ‘screen, another

entered the. screen’in. a:few seconds: The primary.~

tasks: iave: been” described’. more. completely
elsewhere “Thackray and Touchstone, 1989).

a The’ “secondary” task, the detection of tri-
: angular’ targets’ representing ‘nontracked: aircraft,

was the test of primary experimental ‘in

‘ The triangles were similar in size to’ dots “that
possible: conflict situation. Any time a possible -

were added -to the display to: produce clutter:
Triangles could appear at any’ 1 of.8 different
locations; 4 of the locations were: near athe
extreme corners of the display and 4 were-niore

and a typical pattern of alphanumeric targets as

tepresenting controlled aircraft and their

‘blocks. The triangles “representing

aircraft were presented as either red or. gréen.

~ Whenever a VFR target was detected, a: console

button was "pressed and : the’ ‘target would!
disappear shortly thereafter. A: target would: Also
disappear if not detected within a .90-second:
timeout period. =

Figure 1

- Subject’ 's-display showing clutter, “all ‘triangle locations, . : :
and: atypical pattern of alphanumeric targets. ot



Table 2

Mean Detection Time for Green and Red
Triangles as a Function of Color Vision

Green Triangles

95% Confidence
Group Mean S.D. Interval
Normal 11.77 10.78 2.76 to 20.78
Protaa 13.05 15.28 0.27 to 25.82
Deutan 11.37 7.98 4.75 to 18.11
Red Triangles

95% Confidence
Group Mean S.D. interval
Normal 4.72 6.91 -1.05 to 10.50
Protan 15.11 17.26 .67 to 29.54
Deutan 4.23 3.81 1.04 to 7.43

Table 3

Difference Between Detection Times for Green and Red Triangles
in Each Color Vision Group

Green-Red
Group Difference (SEC) T DE P
Normal 7.05 2.41 7 .02*
Protan -2.06 0.24 7 40
Deutan 7.14 2.16 7 03*
*Significant at the .10 level, i-tailed test
Table 4
Differc..e in Detection Times Between Color Vision Groups
Green Triangles Difference (SEC) T DF P
Normal - Protan -1.28 19 12.6 42
Normal - Deutan 46 07 12.9 47
Deutan - Protan -1.68 -26 10.6 39
Red Triangles
Normal - Protan -10.39 1.58 9.2 .07*
Normal - Deutan 49 17 10.9 43
Deutan - Protan -10.88 1.73 77 -06*

*Significant at the .10 level, 1-tailed test


Eighteen primary task and 4 secondary task
critical events occurred during a 60 minute
experimental test session, with no more than 1
event present at any given time. Time of
occurrence of each type of event was fixed.
Location of each successive secondary task
target, however, was randomly assigned without
replacement for each subject. Thus, although
interstimulus intervals were fixed for triangular
targets, the order of locations differed for each
subject. Subjects were given no izformation
regarding the frequency of events or their order
of occurrence. Two video cameras were used to
monitor both the subject’s facial orientation and
the visual display to enable analysis of the
subject’s visual behavior during times when
secondary targets were presented. Ambient
illumination (23 lux at the display) was
comparable to the lighting of the radar displays
measured at an en route center.

Color and Luminance Measurement and
Specification

All color and luminance measurements were
made using a Photo Research spectroradiometer.
The particular red and green colors used were
selected from the available DEC VS11 colors and
were chosen to be as close as possible to the CIE
coordinates (red X=.650, Y=.336; green
X=.329, Y=.600) specified for the FAA’s
Advanced Automation Sector Suites that are
currently under development. While it was not
possible to achieve a perfect match of the
red/green luminances with the VS-1! display,
luminances of the colors selected were reasonably
close. Color and luminance values are shown in
Table 1, The luminance of the red color was
unavoidably 30% higher than the green.

Table 1

Color and Luminance Values of Display Elements

Display CIE Luminance
Elements Hue Coordinates (in foot-
x Y lamberts)
Alphanumerics Green .233 .628 4.94
Clutter Green .233 628 4.94
Triangle Green .233 .628 4.94
Triangle fied 615 342 6.72



: "Was not detected: within a predetermined time .

limit, a “conflict’ alert". occurred signifying a

: , possible: conflict situation. Anytime a possible -

conflict was. detected, either by the subject or
a “conflict-alert”. alarm, the subject had
whether a conflict existed ‘or -not

‘toward’:each other, or not). For: both types of

Ctiticalevents’ in’ the primary ‘task, ‘subjects’

performed appropriate’ Fesponses to resolve the
problems: : ‘Subjects. wee. always controlling 16.
-. aitcraft; ‘when one left the screen, another

: entered the. screen’ in. a:few: seconds: The primary.~

©. tasks: ave. been” described’ more completely
elsewhere‘ ‘Thackray and Touchstone, 1989).

: The" “secondary” task, the detection of tri-
“angular targets* representing ‘nontracked aircraft,

_ was the ‘test of primary experimental interest.

blocks. The | triangles ‘representing -intrud

! disappear shortly thereafter. A target would:dlso

The triangles were similar in ‘size to dots: that

locations; 4 of the locations were: néar .the
extreme corners of the display and’4 were.miore.“~”
centrally located. Figure 1. shows all of: the --;
possible triangle locations as well as the clutter ~..

and a typical pattern of alphanumeric targets ~~‘
tepresenting controlled aircraft .and their ‘data ~

aircraft were presented as either red or. gtéen.
Whenever a VFR target was. detected,-a console ah
button was pressed and the target would’ :

disappear if not detected within a 90-seconid hase ;
timeout period. *

-Subject’s display showing clutter, all triangle locations,
"| ‘and-a-typical pattern of alphanumeric targets.



a 3
oe CO

SONOO3S


AD-A246 586
ET

DOT/FAAIAM-92/6

Office of Aviation Medicine
Washington, D.C. 20591

This ducument has been
for public release and walens
tion is unlimited,

(2)

Effects of Coler Vision Deficiency
on Detection of Color-Highlighted
Targets in a Simulated Air Traffic
Control Display

Henry W. Mertens
Richard I. Thackray
Mark Touchstone

Civil Aeremedical institute
Federal Aviation Administration
Oklahoma City, Oklahoma 73125

January 1992

Final Report

This document is available to the public
through the National Technical Information
Service, Springfield, Virginia 22161.

U.S. Department
of Transportation

Federai Aviation
Administration

92-04810
ea



accord with the experimental hypothesis and can
be attributed to the well known reduced
sensitivity of protans to red light, in combination
with their reduced color discrimination ability as
red-green deficients. Although severe devtans
have reduced color discrimination, they do not
usually have reduced sensitivity. Their
performance did not show any reduction
compared with normals in the effectiveness of
redundant color coding, which was contrary to
our prediction. Although this indicates possible
beneficial effect of color coding, it is also
possible that the 30% greater brightness of red
targets may have counteracted the effect of
reduced color discrimination in the deutans. If
the present display had involved a luminance of
ted that was egual to or less than green, we
could predict that the impairment in detection of
red targets by severe protans would be greater,
and that the benefit of red highlighting would
also have been diminished in severe deutans.

These results demonstrate chat the approach of
using color always as a redundant cue to ensure
performance of color deficients is valuable, but
the potential for adverse interaction of color
coding with color deficiency must always be
considered. These findings also suggest that use
of the color red for highlighting may not be
appropriate when severe protans are in the user
population for the display.

CONCLUSIONS

* The effectiveness of red highlighting used as
a redundant cue for attention-getting is
diminished in individuals with severe protan
color vision deficiency.

@The alerting value of redundant red
hightighting was not diminished in deutans,
relative to normals, in the present study.
Luminance was confounded with color in the
present study, however, and may have
counteracted the effect of reduced color
discrimination in deutans.

@The present findings support the need for
further research to evaluate possible differences
between individuals in color display effectiveness
because of differences in color vision ability.

REFERENCES

Carter, R.C. (1982). Visual search with color.
Journal of Experimental Psychology: Ruman
Perception and Performance, 8, 127-136.

Carter, E.C. and Carter, R.C. (1981). Color
and conspicuousness. Journal of the Optical
Society of America, 71, 723-729.

Christ, R.E. (1975). Review and analysis of
color coding research for visual displays.
Hunian Factors, 17, 542-570.

Cole, B.L. and Macdonald, W.A. (1988).
Defective colour vision can impede
information acquisition from redundantly
colour-coded video displays. Ophthalmology
and Physiological Optics, 8, 198-210.

Federal Aviation Administration. (1985).
Advanced automation system, system level
specification, design competition phase.
Washington: FAA, Evalu. “ion Report, FAA-
ER-130-005F with SCN.

Pokorney, J., Smith, V.C., Verriest, G., and
Pinckers, A.J.L.G. (1979). Congenital and
acquired color vision defects. New York,
NY: Grune and Stratton.

Society of Automotive Engineers (1988). Human
engineering considerations in the application
of color to electronic aircraft displays.
Aerospace Recommended Practice, No.
4032. Warrendale, PA: Society of
Automotive Engineers.

Thackray, R.I. and Touchstone, R.M. (1990).
Effects of high and low taskioad on
detection of flashing and colored radar
targets. OAM Report No. DOT/FAA/AM-
90/3. Oklahoma City, OK: FAA Office of
Aviation Medicine, Civil Aeromedical
Tasticute.

Thackray, R.f. and Touchstone, R.M. (1989).
Effects of high visual taskioad on the
behaviors involved in complex monitoring.
Ergonomics, 32, 27-38.

Wyszecki, G. and Stiles, W.S. (1982). Color
Sceence: concepts and inethods, quantitative
data and formulae, 2nd Edition. New York,
NY: Wiley.

*U.S.GP0:1992-661-063/40027


a) ALTITUDE MALFUNCTION EVENTS

8-4

84
Q
PG
Q

1 i |

54

NORMAL PROTAN DEUTAN
30 MINUTE PERIODS
b) CONFLICT/NOCONFLICT EVENTS

44

$4
:
3 74
wo
a

14

o-

NORMAL PROTAN DEUTAN
30 MINUTE PERIODS
Figure 3

fa) Mean Detection Times for Altitude Malfunction
Events for Each Color Vision Group

(b) Mean Frequencies with which Detection Times for Conflict/No Conflict
Events Equaled or Exceeded 26s for Each Color Vision Group

~



Procedure

Subjects received detailed training for each
type of task event along with the appropriate
responses to each. Short prevtice sessions
followed the description of each type of event,
and a final combined session provided practice
on all primary and secondary task events and
also familiarized subjects with the conflict alert
alarm.

Following the practice sessions, subjects
completed a 9-point subjective rating scale to
describe their present feelings of attentiveness,
tiredness, strain, boredom, and irritation. The
final set of task instructions explained that the
conflict alert alarm was essentially the same as
that used in contemporary ATC systems to warn
controllers of possible conflict situations, and that
in this particular experiment, the alarm would go
off whenever the computer determined that they
had failed to detect a possible conflict in the
minimal allowable time. Subjects received a
bonus contingent upon the number of conflict
alerts that occurred during the experimeutal
session. Background noises recorded in actual air
traffic control radar rooms played continuously
during the experimental testing session. At the
completion of the session, subjects were
administered a second version of the rating scale
that contained additional items relating to
perceived task difficulty and the amount of effort
tequired to maintain task concentration; debrief-
ing concerning the purposes of the experiment
followed.

RESULTS
Detection Times for VFR Intruder Targets

Missed appearances of VFR intruders were
rare. Only 2 intruder targets were missed during
the !-hour experimental session, both by protans.
One missed intruder target was of green color;
the other was red. Those 2 events involving
missed targets were arbitrarily assigned a value
of 90-seconds (the time limit for detection), and
were averaged in with detection latencies in order
to yield a single overall measure of detection
performance. Mean detection latency for the 1-
hour experimental session is shown in Figure 2

as a function of color of VFR intruder targets
(green and red triangles) and color vision
deficiency. The corresponding standard
deviations and 95% confidence limits of detection
times for the 3 vision groups are shown in Table
2. The specific experimeatal hypotheses con-
cerning lack of difference between color vision
groups in detection of green intruder targets, and
the beneficial effects of red highlighting in
normals and individuals with color vision
deficiency were evaluated by planned compari-
sons using t-tests and are shown in Tables 3 and
4. There were no significant differences among
the 2 color vision groups in detection of green
triangles. Detection times were significantly
shorter for red triangles than for green in both
normals and deutans. Detection times were
longer for red triangles in protans, but not
significantly so.

As mentioned above, only protans missed
triangles; normals and deutans missed none.

Primary Task Perfermance

Mean frequency of occurrence of conflict
alerts is shown in Figure 3 as a function of color
vision. Statistical analyses of these data revealed
no significant differences as a function of color
vision classification.

Mean times to detect altitude malfunction
events for subjects in the 3 Color Vision Groups
are also shown in Figure 3. Again there were no
significant effects of color vision classification.

Subjective Data

Although all 3 groups exhibited a decline in
attentiveness, accompanied by increases in
tiredness, strain, boredom, irritation, and effort
from beginning to end of the session, there were
No significant differences between color vision
grcups in the subjective data.

DISCUSSION

The most important finding of this study
concerned the failure of protans to benefit from
the alerting effect of red highlighting of symbols
tepresenting intruder aircraft. That effect is in


EFFECTS OF COLOR VISION DEFICIENCY ON DETECTION OF
COLOR-HIGHLIGHTED TARGETS IN A SIMULATED
AIR TRAFFIC CONTROL DISPLAY

INTRODUCTION

Advanced aviation systems are increasingly
using color coded electronic information displays.
Their inherent flexibility and utility is in large
part due to benefits derived from color coding.
Color can be used for decluttering and organizing
information in displays, as well as for coding and
enhancement of display esthetics (Christ, 1975;
Silverstein and Merrifield, 1986; Society of
Automotive Engineers (SAE), i988). The
attention-getting value of color hightighting is
another important benefit demonstrated in studies
of visual search (Carter and Carter, 1981;
Carter, 1982). It has also been suggested,
however, that the attention-getting value of color
in electronic displays may be reduced in
individuals with defective color vision; while
others have argued that by using color always as
a redundant cue, the performance of color
deficients can be protected (Silverstein and
Merrifield, 1986; Cole and Macdonald, 1988).
This study sought to explore further the potential
for adverse effects of color vision deficiency on
potential conspicuity gains from  color-
highlighting in detection of nontracked VFR
aircraft unexpectedly intruding in controlled
airspace. The symbols concerned with other
monitoring tasks performed simultaneously, and
"clutter" normally present in the simulated ATC
traffic display, were green. The detectability of
red highlighted symbols was compared to green
symbols in the task of detecting intruders.

Predictions

© Detection times among both normals and
color deficients would be similar for green, non-
highlighted intruder symbols.

© Detection times among normals would be
significantly lower for detection of red
highlighted intruder symbols than for green.

© Effectiveness of red highlighting would be
somewhat impaired in deutans, relative to

normals, because of reduced apparent color
difference between red and green.

@ Effectiveness of red highlighting would be
considerably diminished in protans, relative to
normais, because of their well-known reduced
sensitivity to red light (Wyszecki and Stiles,
1982) in combination with reduced color
discrimination ability.

METHOD
Subjects

Eight subjects with normal color vision, 8
having severe coior vision deficiencies of the
protan type, and 8 having severe deficiencies of
the deutan type were selected. In both the protan
and deutan groups, half of the 8 subjects in each
group were diagnosed as extreme anomalous
trichromats and half were dichromats. All were
college students 18 to 29 years of age, with at
least 20/30 acuity, and they were paid an hourly
wage. The color vision diagnosis was performed
with the Nagel Type I anomaloscope (Schmidt-
Haensch) using the Linksz procedure (Pokorney,
et al, 1979). Half each of both protans 2nd
deutans were extreme anomalous trichromats and
the remainder were dichromats.

Apparatus and Task Description

The ATC display was generated by a Digital
Equipment Corporation (DEC) VS11 19-inch
(49-cm) graphics monitor controlled with a VAX
11/730 computer. The primary task consisted of
monitoring for 2 types of critical events. The
first type was readily detectable and consisted of
the appearance of 3 X’s in place of the three
altitude numbers in a given data block. Subjects

were told that the 3 X’s signified that a ....

malfunction had occurred in an aircraft’s altitude

transponder. The second type of critical event —_W....

was considerably more difficult to detect because
it was not immediately apparent: 2 aircraft at the
same altitude on the same flight path. If the event

f

! a ett Special
el

aur



Technical Report Documentation Page

T. Report No. 2. Government Accession No. 3. Recipient's Catalog No.
AM-92/6

4. Title and Subtitle 5. Report Date

Effects sf Color Vision Deficiency on Detection of January 1992
Color-Highlighted Targets in a Simulated Air Traffic 6. Performing Orgonization Code

Control Display

8. Performing Organization Report No.

7. Author's)

Henry W. Mertens, Richard I. Thackray, Mark Touchstone

9. Performing O:ganizotion Name ond Address 10. Work Unit No. (TRAIS)
FAA Civil Aeromedical Institute

P.O. Box 25082 TT. Contract or Grant No.

Oklahoma City, OK 73125

13. Type of Report and Period Covered

12. Sponsoring Agency Name ond Address
Office of Aviation Medicine
Federal Aviation Administration

800 Independence Ave., S.W. 14. Sponsoring Agency Code
Washington, D.C. 20591

15. Supplementary Notes

This work was performed under task AM-D-91-HRR-107.

16. Abstract

The present study sought to evaluate the effects of color vision deficiency on the gain in conspicuity
that is realized when color-highlighting is added as a redundant cue to indicate the presence of
unexpected, nontracked aircraft intruding in controlled airspace. Sixteen subjects with severe color
vision deficiency of both protan and deutan types and eight subjects with normal color vision performed
a simulated high-workload air traffic contro! task over a 1-hour period. Displayed information was
normally green. In addition to the primary task, subjects also monitored for occasional intrusions by
light aircraft identifiable on the basis of triangular shape alone or with the color red added as a
redundant cue. The luminance of the red color was also 30% higher. Detection of red targets was
slightly slower than detection of green targets in protans. In contrast, detection was faster with red
targets for both normals and deutan subjects. Impairment in performance of the severe protans with
red highlighting was attributed to their well known reduced sensitivity to red light. Although severe
deutans have reduced color discrimination, they do not usually have reduced sensitivity, and their
performance was probably enhanced by the greater brightness of red targets. These results demonstrate
that the approach of using color always as a redundant cue to ensure performance of color deficients,
is valuable, but the potential for adverse interaction of color coding with color deficiency must always
be considered.

17. Key Words 18. Distribution Statement
Color Vision Deficiency Document is available to the public
Color Coding through the Naticnal Technical
ATC Displays Information Service, Springfield,
Virginia 22161.
19. Security Clessif. (of this report) 20. Security Classif. (of this page) 2H No. of Pages | 22. Price
Unclassified Unclassified i

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



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