Nelda J. Milburn

Civil Aerospace Medical Institute

Federal Aviation Administration

Oklahoma City, OK 73125

June 2004

Final Report

This document is available to the public

through the National Technical Information

Service, Springfield, Virginia 22161.

 

Office of Aerospace Medicine

Washington, DC 20591

DOT/FAA/AM-04/10 A Historical Review of Color 

Vision Standards for Air Traffic 

Control Specialists at Automated 

Flight Service Stations 
NOTICE

This document is disseminated under the sponsorship of

the U.S. Department of Transportation in the interest of

information exchange. The United States Government

assumes no liability for the contents thereof.
i

Technical Report Documentation Page 

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. 

DOT/FAA/AM-04/10 

4. Title and Subtitle 5. Report Date 

A Historical Review of Color Vision Standards for Air Traffic Control June 2004 

Specialists at Automated Flight Service Stations 6. Performing Organization Code 

 7. Author(s) 8. Performing Organization Report No. 

Milburn NJ

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

FAA Civil Aerospace Medical Institute 

P.O. Box 25082 11. Contract or Grant No. 

Oklahoma City, OK 73125 

12. Sponsoring Agency name and Address 13. Type of Report and Period Covered 

Office of Aerospace Medicine 

Federal Aviation Administration 

800 Independence Ave., S.W. 

Washington, DC 20591 14. Sponsoring Agency Code 

15. Supplemental Notes 

Work was accomplished under approved task HRR-522. 

16. Abstract 

This report chronicles several experiments the Civil Aerospace Medical Institute has conducted to 

assess the effects that advances in technology have had on automated flight service station air traffic 

control specialists color identification tasks and the ensuing revisions to the color vision standard and 

verification testing.

17. Key Words 18. Distribution Statement 

Automated Flight Service Station, Air Traffic Control Document is available to the public through the 

Specialists, Color Vision, ATC history, Color Weather National Technical Information Service 

Radar, Color Vision Standards, Work-Sample Tests, 

Color Vision Deficiency 

Springfield, Virginia 22161 

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price 

Unclassified Unclassified 11 

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

1

A HISTORICAL REVIEW OF COLOR VISION STANDARDS FOR AIR TRAFFIC CONTROL

SPECIALISTS AT AUTOMATED FLIGHT SERVICE STATIONS

INTRODUCTION

In conjunction with the celebration of 100 years of 

flight, this report provides a historical overview of the 

technological innovations within the automated flight 

service station (AFSS) facilities that subsequently affected 

the controllers' tasks and increased the demand on their 

color perception ability. Air traffic control specialists 

(ATCSs) at AFSS facilities brief pilots on weather conditions both before and during flights. The good news is 

that the ways in which weather information is obtained, 

coded, and conveyed have evolved from simply making 

out-the-window observations to having immediate access 

to worldwide, detailed weather information, color-coded 

and displayed on high-resolution monitors. As with many 

technological improvements, there are often unforeseen 

consequences that may adversely affect performance. Indeed, this was the case with the implementation of new 

weather displays. After all, there was no need for a color 

vision standard for early-day ATCSs who used teletyped 

textual information or who later used crude, 3-level monochromatic graphical depictions of the weather situation. 

However, as equipment changed, so did the demand on 

color discrimination ability and, consequently, the need 

to verify that ability. 

As a result, the FAA now requires that all applicants 

for ATCS positions demonstrate their color discrimination ability because several ATC tasks involve critical, 

nonredundant, color-coded information. Furthermore, 

technological advancements now allow computers to 

produce 16 million colors. To take advantage of this 

new technology, many weather radar maps use a nonstandardized, 16-level color code to depict various levels 

of reflectivity. Each level is related to the increasing probability of hazardous weather and is coded in shades of 

blue, green, yellow, red, purple, and white.

With the rapid proliferation of computer technology 

and the concomitant ability to utilize color in displays, 

it has become increasingly necessary to develop a color 

vision standard. Toward these ends, the Civil Aerospace 

Medical Institute has been involved in evaluating the 

changing color perception tasks of pilots and controllers 

for more than 30 years. The Civil Aerospace Medical 

Institute has also continually substantiated the need for 

a color vision standard. Furthermore, recommendations 

made to the Federal Air Surgeon derived from periodic 

re-evaluations of the standard necessitated revisions to the 

regulation to keep pace with changing technology. This 

report chronicles several experiments the Civil Aerospace 

Medical Institute has conducted to assess the effects that 

advances in technology have had on AFSS ATCS coloridentification tasks and the ensuing revisions to both the 

color vision standard and verification testing.

HISTORICAL OVERVIEW

In the early 1920s when flight service station air traffic controllers first began providing weather information 

to pilots, there were no air-to-ground communications. 

According to 70 Years of Flight Service, operators “made 

their own weather observations and forecasts, passing 

information to pilots during their ground stops” (Terrana, 

1990, p. 29). Terrana (1991a, 1991b, 1992) chronicles 

the creation of the flight service stations—first known 

as Air Mail Radio Stations—to the AFSSs of today. The 

Weather Bureau, as it was called then, furnished textual 

weather reports that were transmitted to the flight service 

stations via teletype. Although only anecdotal information 

is available, it is believed that most operators converted 

the textual information to national, regional, or local 

hand-drawn maps fairly early. The maps used a colorcoding system that depicted the various levels of weather 

intensities to better conceptualize weather patterns. 

However, in the mid-1960s access to radar imagery 

became available. Using a monochromatic (one color) 

coding scheme, weather could be portrayed in shades of 

gray representing 3 levels of intensity. By the early 1980s, 

“color radar imagery could be accessed from National 

Weather Service radars (WSR-57 and WSR-74) and the 

Federal Aviation Administration (FAA) radars situated 

across the country” (WSI Corp., 2001). Six intensity 

levels displayed in color replaced the gray-coding scheme. 

The new digitized weather product was called the Radar 

Remote Weather Display System (RRWDS) and boasted 

the “most advanced state-of-the-art color weather radar 

display ever produced” with a “high resolution, noninterlace 60Hz raster scan of 512 x 512 pixels” (Talley 

Industries, undated product brochure, p.2). Not only 

could weather level colors be individually selected for 

viewing or masked (hidden), but users could select only 

the most intense weather levels to be shown, thus decluttering the display and emphasizing the most trouble-
2 

some areas. Furthermore, specific colors could be set to 

blink, thus alerting the operator to the presence of that 

particular level. 

At least three RRWDS design aspects added a level 

of redundancy to interpreting the color-coding. Features 

such as zoom, level select, and blinking enhanced color 

perception by increasing size or otherwise isolating specific 

coding and thereby protecting the performance of controllers with normal color vision over the range of viewing 

distances and consequent image size variation. Equally 

important, the redundant design features protected the 

performance of controllers with color vision defects. 

The weather intensity was depicted in 3 colors (green, 

yellow, and red), 2 intensities each, representing levels 1 

through 6 (light, moderate, heavy, very heavy, intense, 

and extreme) as defined by the National Weather Service 

and the National Bureau of Standards. The system provided meteorologists at Air Route Traffic Control centers 

with detailed information on the location and severity of 

weather conditions nationwide by allowing the operator 

to dial-up any of several dedicated radar sites by entering 

its telephone number into a computer keypad. 

During the 1980s, ATCSs experienced several technological changes made at flight service stations that revolutionized their tasks, including the invention of a monitor 

that allowed controllers to exchange their colored pencils 

for a color display of weather maps. Perhaps a carryover of 

the colors used in the paper-and-colored-pencils phase (or 

more likely the limitations of the display) and/or perhaps 

some remote connection to the cultural connotations attached to colors (such as green—go, yellow—caution, and 

red—danger) dictated the colors designated to represent 

each weather level. Regardless of the origin of the colorcoding, by the mid-1980s color weather radar was being 

used to display weather information (see Figure 1).

One of the first color codes in use illustrated bodies 

of water with the color blue and used two shades each of 

green, yellow, and red to represent 6 weather intensities 

on a black background. Basically, 16 colors were possible 

on the CGA (color graphics adapter) monitors with the 

red, green, and blue color guns. The 16 colors were hardwired into CGA displays and consisted of full-intensity 

(light) and half-intensity (dark) versions of the primary 

colors and their combinations, plus white, black, and 

two shades of gray.

Additional technological changes allowed computers to produce 256 colors and, eventually, 16.7 million 

colors. Simultaneously, the resolution on the displays 

improved from 400 x 200 to 1280 x 1024 pixels. The 

improved resolution allowed weather maps to be presented 

in greater detail that more closely represented weather 

patterns. By the mid-1990s, color weather radar product 

suppliers expanded from 7- to 16-levels to represent a 

finer gradation of weather intensities (Table 1). A new 

program from the National Weather Service, called Next 

Generation Weather Radar (NEXRAD), was established 

with the goal of replacing the 128 aging WSR-57/74 

radars in flight service stations across the country. The 

NEXRAD radars, called WSR-88D, were a new Dopplertype that allowed the user to see motion in atmospheric 

conditions. This enabled the user to view cold fronts, 

dry lines, and thunderstorm gust fronts as never before 

possible. A major advantage of NEXRAD was to provide 

early warning in cases of potentially severe weather. These 

technological advances and product improvements not 

only changed the job tasks, but also, presumably, the 

level of color vision ability required in air traffic control 

personnel. Because the older system, the RRWDS, had 

redundant cues available in addition to color that the 

new systems did not, the new systems required the user 

to rely more heavily on the color-coded information for 

interpretation. For those reasons, confirmation of one’s 

ability to interpret the color-coded information became 

necessary, thus leading to a color vision standard and, 

subsequently, the need for a color weather radar worksample test. 

Color Vision Standards for All Controllers

Applicants for Federal Aviation Administration ATCS 

jobs in en route centers, terminal towers, and flight service 

stations were required to demonstrate their color vision 

discrimination ability as early as 1978, when Medical 

Guideline Letter Number B-5A-0002 was written. It 

required normal color vision for all ATCSs because a 

number of ATCS tasks involved critical, nonredundant, 

color-coded information. The following are ATCS tasks 

involving color-coded information identified by job analysis in the mid-1980s and used in subsequent research 

Figure 1. Radar Remote Weather Display System 

(RRWDS)
3

(Adams & Tague, 1985; Lahey, Veres, Kuyk, Clark, & 

Smith, 1984; Lahey, Veres, Kuyk, & Clark 1984; Mertens, 

1990; Mertens, Milburn, & Collins, 1995, 1996, 2000; 

Pickrel & Convey, 1983):

1. Reading of red and black printing and also red and black 

(or blue) handwriting on flight progress strips used by 

ATCSs at en route facilities.

2. Scanning of color weather radar displays at en route centers 

and AFSS facilities. Blue, green, yellow, red, purple and 

white indicate different weather levels.

3. Identifying an aircraft’s direction at night by tower controllers both while it is in the air and on the ground. 

Identification is based on red, green, and white navigation 

lights.

4. Identifying the color of the Aviation Signal Light indicator 

that gives a tower ATCS visual feedback concerning the 

signal light color (red, green, or white) that is used to direct 

an aircraft or ground vehicle when radio communication 

fails or is not available.

5. Identifying aircraft by the color of aircraft or its markings 

from within air traffic control towers in the daytime.

6. Reading a variety of color-coded charts at all types of 

facilities.

7. Selecting the appropriate colored indicator lights, keys, 

switches, and buttons at all types of facilities.

Not all of the above listed tasks are relevant to AFSS 

ATCSs. Furthermore, some of the tasks involve redundantly color-coded materials that would allow a person 

with color vision deficiencies to operate or interpret the 

meaning of the color-coding based on the availability of 

the redundancy. The built-in redundancies guard against 

misinterpretation of the simple color-coding. Tasks 5, 

6, and 7 listed above have some built-in redundancy; 

and therefore, color-coding has a secondary importance. 

However, tasks 1 through 4 rely heavily or entirely upon 

color-coding to convey meaning to the user for interpretation. The primary color-related tasks include interpreting 

color coding on flight progress strips, aircraft navigation lights, and color weather radar images on a cathode 

ray tube (CRT). Most relevant to flight service is color 

weather radar. 

Given the number of critical tasks that require ATCSs 

to decipher the meaning of the color-coded material, it is 

not surprising that “normal color vision” was a pre-employment job requirement. In this context, normal color vision 

refers to the way approximately 95+% of the population 

sees colors. Estimates vary, but about 8 to 10% of all males 

and about one-half of 1% of females see colors differently 

than the majority of people (Wyszechi & Stiles, 1982). 

Because a very high percentage of the population match

Table 1 

Comparison of 7-Level WSR-57 to the 16-Level WSR-88D Weather Intensities a

Precipitation Intensity Levels 

Refectivity 

 Levelb WSR-57 WSR-88D 

 Approximate 

Rainfall Rate 

 

5-10 Level 1 Drizzled

10-15 Level 2 Light snowd

15-20 Level 3 Light snowd

20-25c Level 1 Light Level 4 Light .02”/hour 

25-30 Level 1 Light Level 5 Light .02”/hour 

30-35 Level 2 Moderate Level 6 Moderate .09”/hour 

35-40 Level 2 Moderate Level 7 Moderate .09”/hour 

40-45 Level 3 Heavy Level 8 Heavy .48”/hour 

45-50 Level 4 Very Heavy Level 9 Very Heavy 2.5”/hour 

50-55 Level 5 Intense Level 10 Intense 5.7”/hour 

55-60 Level 5 Intense Level 11 Intense 5.7”/hour 

60-65 Level 6 Extreme/Hail Level 12 Extreme/Hail 12.9”/hour 

65-70 Level 6 Extreme/Hail Level 13 Extreme/Hail 12.9”/hour 

70-75 Level 6 Extreme/Hail Level 14 Extreme/Hail 12.9”/hour 

>75 Level 6 Extreme/Hail Level 15 Extreme/Hail 12.9”/hour 

a original source of tabled information unknown 

b measured in dBZ

c

18-25 dBZ for WSR-57 

d precipitation may not be hitting ground 
4 

colors in a similar way, they are said to have normal color 

vision. In contrast, those persons who see colors differently are labeled as color vision deficient. The incidence 

of color vision deficiency occurs across ethnic groups with 

the prevalence varying but with Caucasian males showing 

the largest ratio of red-green color vision deficients (Hunt, 

1998; Pokorny, Smith, Verriest, & Pinckers, 1979). The 

initial, normal color vision pre-employment job requirement remained in effect until the Equal Employment 

Opportunity Commission regulation (29 C.F.R. Section 

1613.705a) was written. It stated that an agency could 

not make use of any employment test that screens out 

qualified handicapped persons unless it is shown to be 

job-related for the position in question. Consequently, 

the first step was to substantiate the need for a color vision requirement. Justification for the screening test was 

based on its job-relevance, especially the non-redundant 

nature of color-coding in some ATCS tasks. However, 

making the connection between color vision screening 

test results and performance involving on-the-job tasks 

was harder to establish when the screening test was not 

composed of actual ATCS materials and/or tasks. At that 

time, the determination of normal color vision and one’s 

capability of performing the color-related tasks was based 

on passing a pseudoisochromatic plate (PIP) test. 

Need for Work-Sample Color Vision Tests

A court decision in 1980 determined that PIP tests were 

medical tests designed to measure genetically determined 

variations of color vision among individuals. Notably, 

the PIP tests do not predict the potential satisfactory 

performance of air traffic control duties related to color 

vision. This is an important point because the requirement that the applicant must have normal color vision 

should be interpreted to mean that the individual must 

be able to function normally in recognizing colors in the 

work environment. Consequently, the court found that 

ATCS applicants who did not pass the PIP tests should 

be given the opportunity to demonstrate their ability to 

recognize colors using work-sample materials.

In 1981, the Office of Personnel Management undertook an “examination of ATCS job requirements 

for color vision, asking nearly thirty ATCSs to list tasks 

that might require them to be able to distinguish and/or 

name colors” (Pickrel & Convey, 1983, pp. 4-5). From 

that list, “simulations of ATC tasks were created in three 

content areas: 1) aircraft colors for fuselage and lights, 2) 

color weather radar displays, and 3) navigational chart 

terrain elevations” (ibid., p. 5). The sub-tests consisted of 

color-identifications on ATCS task simulations and were 

assembled in a loose-leaf notebook requiring a paperand-pencil answer sheet. The speeded test was called the 

Air Traffic Controllers Functional Color Perception Test 

(ATC-FCPT, Pickrel & Convey, 1983; Convey, 1985). 

Later, the ATC-FCPT was combined with the Dvorine 

Pseudo-Isochromatic Plates test and the Farnsworth D15 test. Both of the latter tests used special disposition 

criteria, fully described in Mertens (1990). The resulting 

“Three-Test Battery” was then recommended by the FAA’s 

Office of Aviation Medicine to test ATCS applicants who 

had failed their initial aeromedical color vision test. The 

scoring criteria for the Dvorine PIP (failure with 5 or 

more errors) and the special scoring procedure for the 

D-15 were based on recommendations of Lahey, Veres, 

Kuyk, Clark, and Smith (1984), who provided an indepth “Job Analysis and Determination of Color Vision 

Requirements for Air Traffic Control Specialists” for the 

Office of Personnel Management. 

In December 1985, the FAA’s Medical Guideline 

Letter Number B-5a-0061 established a procedure for 

“Testing of ATCS Applicants Appealing Disqualification 

for Color Perception Deficiency.” To be considered for 

employment as an ATCS, an applicant had to pass 2 of 

the 3 tests constituting the battery. That pass criterion 

was based on reports by Lahey, Kuyk, Veres, and Clark, 

(1984); Lahey, Veres, Kuyk, Clark, and Smith (1984); 

Pickrel and Convey (1983); and Convey (1985).

Re-Evaluation of the Work-Sample Test

Several years later, the Three-Test Battery was included 

in a study designed to determine the relationship between 

errors in performance of simulated ATCS color tasks 

and color vision deficiency “in order to evaluate the 

level of color vision ability required in ATCS personnel” (Mertens, 1990, p. 2). The Mertens study included 

all aeromedical color vision screening tests in use (in 

1988) “by Aviation Medical Examiners (AMEs) for the 

initial medical examinations of ATCSs and pilots” (p. 

4). The experiment included 9 PIP tests, 3 lantern tests, 

and 4 vision testers--all listed in the then current FAA 

Aviation Medical Examiner’s Guide (1980). The study 

compared pass/fail performance on each of the FAA-accepted tests, the Three-Test Battery as a whole, and each 

of its component tests separately, to 4 simulated ATCS 

color-identification tasks: Flight Progress Strips, Color 

Weather Radar, Aircraft Lights, and Aviation Signal 

Lights. That study also used actual flight progress strips 

obtained from an en route center to serve as a criterion 

(work-sample) test to examine the predictive validity of 

the Three-Test Battery and other FAA-accepted tests. The 

study made a substantial contribution by analyzing performance on simulated ATCS tasks as a function of type 

and degree of color vision deficiency. Most importantly, 

findings from the study negated previous opinions about 

individual test performance and the predictive quality of 

each test—especially the Three-Test Battery. Although 
5

performance on the ATC-FCPT was poor, it was most 

likely because it was a cognitively difficult, timed test 

that was not strictly a color-perception test. 

Based on results from Mertens’ (1990) original study 

and a later replication study (Mertens & Milburn, 1992a), 

a new directive from the Federal Air Surgeon was written instructing regional flight surgeons to administer the 

Dvorine PIP, rather than the Three-Test Battery, to all 

individuals seeking initial employment with the FAA as 

ATCSs. In addition, the Medical Guideline letter described the course of action to be taken in the event an 

applicant failed the Dvorine PIP. Specifically, it stated that 

the applicant would be “notified of their opportunity to 

be re-evaluated” (MGLRM, 1995, MGL-87, p. 3).

The guidance stated that applicants who desired reevaluation would be presented a repeat administration 

of the Dvorine PIP under standardized conditions. If no 

more than 2 errors were made, the person was passed 

and no further testing was required. The applicant thus 

qualified for all ATCS options. Otherwise, if the applicant 

failed the Dvorine PIP, the practical test that applied to a 

specific work option had to be passed for the applicant to 

be considered for that work option. The Aviation Lights 

Test (Figure 2) is the work-sample test for ATCSs wishing to work in the terminal option. The Flight Progress 

Strips Test (Figure 3) applies to the en route (or center) 

option and is composed of several flight progress strips 

lithographed onto the same green ledger paper used in 

the field. The notable difference is that in the Aviation 

Lights Test, the applicant identifies red, green, and white 

lights that meet the FAA (1988) and ICAO (1988) standards; whereas the Flight Progress Strips Test requires the 

identification of red and black printing. 

Need for a Work-Sample Test for AFSS

At the time MGL-87 was issued, only the practical 

tests for the en route (center) and terminal options had 

been developed. Consequently, MGL-87 stated that an 

alternative color perception test for the flight service station option was under development at the Civil Aerospace 

Medical Institute. “Until another test is adopted, applicants for the flight service station option must successfully pass the Dvorine pseudoisochromatic plate test by 

making no more than two (2) errors under standardized 

conditions” (MGLRM, 1995, MGL-87, p. 3).

By 1993, in compliance with the above-mentioned directives from the Office of Personnel Management, the Equal 

Employment Opportunity Commission, and the Federal 

Figure 2. Aviation Lights Test Air Surgeon, two practical (job-sample) tests had been 

Figure 3. Flight Progress Strips Test
6 

developed to allow ATCS applicants who failed their initial color vision screening the opportunity to demonstrate 

their color-vision abilities using simulated ATCS materials. 

Specifically, the color-related tasks described in Task 1 above 

were carefully reproduced in the Flight Progress Strips 

Test; and, similarly, Tasks 3 and 4 were simulated in the 

Aviation Lights Test (Mertens, 1990; Mertens & Milburn, 

1992a; Mertens, Milburn, & Collins, 1996, 2000). Because 

Tasks 5, 6, and 7 have some inherent redundant coding 

available to the ATCSs to aid interpretation, only the task 

related to deciphering the color coding on a weather radar 

CRT had not been accomplished. Accordingly, Task 2 was 

addressed in an initial laboratory depiction of the AFSS 

color weather radar display that involved two concentric 

squares with the inner square representing the target color 

and the outer square representing various background or 

surround colors (Mertens, 1990). In that experiment, two 

target sizes were evaluated (0.1 and 0.5 degrees), but only 

1 color palette measured at the McAlester, OK, AFSS 

containing 7 color-coded weather levels was duplicated 

in the laboratory. The participant’s task was to identify 

the color of the inner square by color name and intensity 

such as light or dark--green, yellow, or red. All colors and 

intensities served as target and surround colors, and all 

combinations were presented. The targets were presented 

on 2-in squares on a black CRT screen. The small target 

size was used because discussions with AFSS ATCSs and 

meteorologists working at FAA facilities indicated that 

being able to identify the color of very small areas on a 

color weather radar display is important. In the laboratory, 7 of 31 participants with normal color vision made 

at least 1 color identification error on the 0.1-degree target 

(Mertens, 1990). However, the current weather displays 

used by ATCSs allow the user to “zoom” the weather image 

at any location on the display and thus enlarge the target 

to several times its original size. In defense of the small 

target size, the user must recognize a potentially hazardous 

area as such, to know to enlarge that area, leading to the 

conclusion that recognition of a small color-coded area is 

a prerequisite to prompt enlargement of the area. 

Since that experiment, technological changes have 

allowed weather image providers to market improved 

products to AFSSs and, in turn, the technological advances have changed the demands on the user’s color 

perception. One such product change occurred when 

weather image providers expanded the color coding from 

7 levels to 16 in the NEXRAD system. Not only were new 

colors added to the original coding scheme, (e.g., blue, 

purple, and white), but several intensities of each color 

were possible. Although some composite radar displays 

using 7 levels are still in use, the 16-level weather product 

has gained wide acceptance because it more precisely 

depicts the weather situation. The National Weather 

Service generates weather information and/or radar images. From that information, a few companies produce 

color-graphic weather images that the FAA purchases. 

Each company is free to develop its own color palette 

for coding the weather levels. Additionally, some AFSSs 

locally produce some types of weather images that are 

unique to that particular facility.

Challenges and Design Issues of a CRT-Based Color 

Vision Test 

One can quickly understand that creating a computerized color vision test that will re-create the AFSS ATCS’s 

color discrimination tasks (relevant to Task 2) will present several challenges including accurately duplicating, 

on laboratory equipment, the colors that were measured 

at various AFSS field facilities. An initial survey revealed 

that each field facility uses a variety of brands and sizes of 

monitors. Because each CRT monitor has several adjustments available to the user such as brightness and contrast 

that act in conjunction with the individual limitations and 

capabilities of the monitor, color appearance differences 

exist between monitors. (This is similar to the differences 

apparent between television sets in a department store 

showroom.) Therefore, it is necessary to evaluate the effect 

on color perception as measured by test performance as a 

result of using different monitor brands, ages, sizes, and 

adjustments (with a specifically designated color card). 

The second challenge will be producing a test with 

a clear, understandable task that captures the essence of 

the ATCS color-identification task that can be performed 

by applicants who have not received any ATCS training. 

The test has to be strictly a color vision test. 

The third challenge of creating a computerized color 

vision test will be assuring that the colors used in the 

laboratory for test development and validation can be 

accurately reproduced on the CRTs at field testing sites. 

The CRTs must be calibrated on site just before testing 

with small tolerances specified for the chromaticities 

used in the test.

An important design issue will be selecting an appropriate target size for test trials of the color weather radar 

test. Previous work on the topic of target size revealed 

“the occurrence of some errors in normal trichromats... 

under adverse observation conditions in the flight strips 

and radar tasks...for identification of small targets on 

the order of 0.1 deg in size on radar displays” (Mertens, 

1990, p. 8). 

The next steps will involve selecting sets of color palettes for examination, creating an initial set of test trials, 

ensuring content validity, developing a scoring strategy, 

and establishing a pass/fail criterion. The final step will 

involve comparing performance on the Color Weather Radar Test to the Dvorine PIP as a function of anomaloscope 
7

diagnoses with its purpose being to identify individuals 

who fail the initial color vision screening test and who 

perform similarly to people with normal color vision on 

the work-sample test. Previous studies (Mertens, 1990; 

Mertens & Milburn, 1992a, 1992b; Mertens, Milburn, 

& Collins, 1998) reported high predictive validity values 

for the Dvorine PIP test (all reporting Kappas near .90) 

for simulated ATCS color-identification tasks. As with the 

practical color vision tests for the en route and terminal 

options, a few people were able to perform the work-sample 

tasks but were unable to pass the Dvorine PIP screening 

test. Mertens (1990) reported false-positive rates ranging 

between 7.1% and 35.8% for the Dvorine PIP test for 

prediction of performance on the 7-level color weather 

radar tests using small and large targets, respectively. 

CONCLUSIONS

This paper has provided a historical review of the 

technological changes that have affected the coloridentification tasks of the AFSS ATCSs and the subsequent 

changes to the color vision standards and testing materials. 

Furthermore, the paper introduces the challenges relevant 

to the development of a work-sample color vision test 

intended to allow AFSS ATCS applicants the opportunity 

to demonstrate their color vision ability while performing 

CRT-related color weather radar tasks. Specifically, the 

challenges and initial decisions include selection of an 

appropriate target size, size of monitors, brand of monitors, characteristics of the color palettes, number of colors 

used, and the presence or absence of a color legend. 

Future Issues

Although the initial goal of using color on displays 

was to declutter, speed, and simplify the interpretation 

of textual information, now the number of codes possible 

are almost limitless by combining 16.7 million colors 

with many other display techniques (e.g., reverse video, 

flashing, brightness contrast, text size, and font). This 

is important because it has the potential to complicate 

the use of color displays by providing an overwhelming 

amount of information. So now, not only is color perception a vital issue but also the overall complexity of the 

color-coded display.

As additional uses of color are introduced by new 

advanced technologies entering the ATC terminal, automated flight service, and en route environments, clinical evaluations of the resulting changes to those ATCSs’ 

knowledge, skills, and abilities must be conducted. Ultimately, as long as technology continues to change the 

controller’s color identification job tasks, the work-sample 

testing materials used to verify the applicant’s ability must 

also be dynamic to keep pace.

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