Practical color vision tests for air traffic control applicants: en route center and terminal facilities.

BACKGROUND: Two practical color vision tests were developed and validated for use in screening Air Traffic Control Specialist (ATCS) applicants for work at en route center or terminal facilities. The development of the tests involved careful reproduction/simulation of color-coded materials from the most demanding, safety-critical color task performed in each type of facility. METHODS: The tests were evaluated using 106 subjects with normal color vision and 85 with color vision deficiency. The en route center test, named the Flight Progress Strips Test (FPST), required the identification of critical red/black coding in computer printing and handwriting on flight progress strips. The terminal option test, named the Aviation Lights Test (ALT), simulated red/green/white aircraft lights that must be identified in night ATC tower operations. Color-coding is a non-redundant source of safety-critical information in both tasks. RESULTS: The FPST was validated by direct comparison of responses to strip reproductions with responses to the original flight progress strips and a set of strips selected independently. Validity was high; Kappa = 0.91 with original strips as the validation criterion and 0.86 with different strips. The light point stimuli of the ALT were validated physically with a spectroradiometer. The reliabilities of the FPST and ALT were estimated with Chronbach's alpha as 0.93 and 0.98, respectively. CONCLUSIONS: The high job-relevance, validity, and reliability of these tests increases the effectiveness and fairness of ATCS color vision testing.

Validity of clinical color vision tests for air traffic control.

BACKGROUND: An experiment on the relationship between aeromedical color vision screening test performance and performance on color-dependent tasks of Air Traffic Control Specialists (ATCS) was replicated to expand the database supporting the job-related validity of 13 FAA-accepted screening tests. METHODS: The original experiment (10) (n = 108), and the replication (n = 136) involved a total of 121 normal trichromats, 31 simple and 44 extreme anomalous trichromats, and 48 dichromats; both protans and deutans were included. The simulations of ATCS color tasks which served as validation criteria were flight progress strips (en route centers), aircraft lights and the Aviation Signal Light indicator (ATC terminal operations), and color weather radar (flight service station and en route center facilities). RESULTS: The validities (Kappa) of aeromedical screening tests ranged from 0.44 to 0.91 for prediction of error-free performance on all color-dependent tasks. CONCLUSIONS: The aeromedical screening tests were generally acceptable in terms of selecting individuals who did not make errors on ATCS color tests, but several tests had high false alarm rates. High job-related validity, in the vicinity of 0.90, was confirmed for several aeromedical color vision tests used for ATCS screening.

Performance of color-dependent air traffic control tasks as a function of color vision deficiency.

BACKGROUND: This experiment was conducted to validate the requirement for normal color vision in Air Traffic Control Specialist (ATCS) personnel who work at en route center, terminal, and Flight Service Station (FSS) facilities. METHODS: A data base was developed involving 121 individuals with normal color vision, 31 simple and 44 extreme anomalous trichromats, and 48 dichromats; both protans and deutans were included. The performance of subjects with normal color vision was compared with the performance of individuals with various classifications of color vision deficiencies on a battery of color-dependent ATCS tasks. Simulations of the ATC color tasks concerned color coding in flight progress strips (at en route centers), aircraft lights and Aviation Signal Light indicator (in tower operations), and color weather radar (at FSS's). RESULTS: Errors were rare among normal trichromats. Mean errors were significantly higher at every level (degree) of color vision deficiency. Approximately 6% of color deficient subjects were able to perform ATC color tasks without error. The 6% were all from the simple anomalous trichromat category; all extreme anomalous trichromats and dichromats were prone to error on ATC tasks. CONCLUSIONS: We conclude that these findings provide support for the requirement of normal color vision in the initial medical screening of ATCS personnel.

Age, alcohol, and simulated altitude: effects on performance and breathalyzer scores.

Trained men in two age groups, 30-39 (n = 12) and 60-69 (n = 13), each performed at the Multiple Task Performance Battery in four separate full-day sessions with and without alcohol (2.2 ml of 100-proof vodka per kilogram of body weight) at ground level and at a simulated altitude of 12,500 ft (3,810 m). Subjects breathed appropriate gas mixtures through oxygen masks at both ground level and altitude. Mean breathalyzer readings peaked near 88 mg% and did not differ between age groups or altitude conditions. Younger subjects performed better than older subjects; performance of both age groups was significantly impaired by alcohol but these adverse effects were greater for the older subjects. No significant effects on performance were obtained due to altitude or to the interaction of altitude with alcohol. These results and those from several other studies suggest that prevalent views regarding the nature of the combined effects of alcohol and altitude on blood alcohol levels and on performance need to be redefined.

Some effects of alcohol and simulated altitude on complex performance scores and breathalyzer readings.

Each of 17 men was trained on 7 tasks in the Multiple Task Performance Battery and then performed over a 2-week period in four experimental sessions: ground level with and without alcohol, and simulated altitude (12,500 ft), with and without alcohol. Subjects breathed appropriate gas mixtures through oxygen masks at both ground level and altitude. Alcohol doses of 100-proof vodka mixed with juice 2.2 ml X kg-1 of body weight. Results showed no differential effect of simulated altitude on breathalyzer readings (peaks averaged 78 mg % at 12,500 ft and 77 mg % at ground level). The best performance occurred at ground level under placebo conditions; the 12,500-ft simulated altitude produced some decrement for placebo scores. Alcohol at ground level resulted in significantly impaired performance during the morning sessions; the addition of altitude to the alcohol condition further depressed performance scores, but to about the same extent that placebo scores were depressed by altitude. Thus, there was no synergistic interactive effect of alcohol and altitude on either breathalyzer readings or performance scores.

Effects of approach lighting and variation in visible runway length on perception of approach angle in simulated night landings.

Previous experiments in this laboratory have demonstrated illusions due to variations in both length and width of runways in nighttime "black hole" approaches. Even though approach lighting is not designed to provide vertical guidance, it is possible that cues from approach lights could interact with cues from runway lighting to reduce illusions due to variation in runway size. Two experiments were conducted to evaluate the effect of approach lighting on perception of approach angle in simulated night approaches. In the first experiment, 40 pilots made simulated visual approaches to a 150- by 6,000-ft runway (45.7-1829 m) with and without a 3,000-ft approach (914 m) light system (ALSF-2). Pilots controlled a moving runway model to produce a constant "normal" angle of approach over the distance range of 23,000 ft (7010 m) to 8,000 ft (2438 m) from threshold. In the second experiment, 24 pilots made simulated approaches to a 150- by 6,000-ft runway which was either fully visible or which had lights of the upwind half occluded. In addition, a 1,400-ft (427 m) abbreviated approach light system (SSALS) was used at three intensities. Decreasing the visible length of the runway by occulting lights of the far half increased mean generated approach angles from 2.2 degrees to 2.7 degrees in agreement with results of a previous experiment involving similar lengths of runways. Neither the presence of equal intensity approach lights nor uncomfortable glare from approach lights 20 times brighter than runway lights had an effect of practical significance on responses. These findings reinforce previous experimental demonstrations of the importance of runway size cues related to varying runway length, and also show that potential size cues provided by approach lights do not prevent illusions due to variations in runway size.

Effect of different runway sizes on pilot performance during simulated night landing approaches.

Both anecdotal reports from pilots and theories of visual cues would predict lower approaches to narrow or long runways than to wide and short runways. Similar, practice approaches made by pilots to a particular width of runway should lead to an increase in subsequent approach angles flown to wider runways and a decrease in approach angles flown to narrower runways. Two experiments with instrument-rated pilots made quantitative tests and these predictions. In Experiment I, three pilots flew simulated approaches and landings in a fixed-base simulator with a computer-generated image visual display. Practice approaches were flown with an 8,000-ft long runway that was either 75, 150, or 300 ft wide; test approaches were to runways with widths or 75, 100, 150, 200, and 300 ft. In Experiment II, 40 pilots controlled the slant of a moving model runway during simulated night visual approaches. Five different models simulated runways from 100 to 300 ft wide and 3,000 to 9,000 ft long. As predicted, training on a wide runway in Experiment I lowered approach angle in approaches to narrower runways; a narrow practice runway also raised approach angles to wider runways. The magnitude of these practice effects increased as distance from runway threshold decreased. There was also a general tendency for approach angles to decrease as runway width decreased. The latter effect was corroborated in Experiment II; in addition, generated approach angles decreased with increasing runway length. Giving half the pilots information about runway size prior to each approach had no effect on responses. These findings add to the quantitative evidence of danger in night visual approaches due to visual illusions and large variability in the visual perception of approach angle.

Physiological biochemical, and performance responses to a 24-hour crash diet.

Twelve overweight male subjects were evaluated on both a normal diet and a 24-h crash diet. During approximately 2 1/4-h complex performance tests subjects breathed an O2/N2 mixture equivalent to 3810 m. (12,500 ft). There were no significant findings due to diet for heart rate, blood pressure, serum electrolytes, subjective fatigue and urinary excretion of K+, epinephrine and norepinephrine. body temperatures were lower (p less than 0.05) for the crash diet than for the normal diet. Serum glucose levels increased during the normal diet and decreased during the crash diet. Hematocrit increased more for the crash diet (p less than 0.05) than for the normal diet. Urinary excretion of 17-ketogenic steroids was less (p less than 0.001) during sleep for the crash diet than for the normal diet. Complex performance showed no significant differences when subjects were tested under low workloads. Performance was enhanced during the crash diet when subjects were tested under the medium and high workload conditions.

Perception of runway image shape and approach angle magnitude by pilots in simulated night landing approaches.

One cue for visual judgments of glidepath angle has been referred to as form ratio. Form ratio is defined as the ratio of vertical height of the runway to width of the far end in the runway retinal image. The ability of pilots to judge form ratios was compared with the ability to judge approach angles in the nighttime "black hole" situation in two experiments. Responses in both static and dynamic simulated approach conditions indicated a general tendency to overestimate form ratios and approach angles less than 3 degrees. Intersubject and intrasubject variability of form ratio and approach angle responses were comparable. These findings (i) do not support the utility of form ratio judgments as an aid in selecting approach angle, (ii) add to the empirical evidence of visual illusions and the danger of reliance on visual information for judgment of approach angle in the nighttime "black hole" situation where only runway light are visible, and (iii) point to variability in perception of approach angle as an important part of the problem.

Pilot performance during simulated approaches and landings made with various computer-generated visual glidepath indicators.

Two simulator experiments were conducted to quantify the effectiveness, in terms of pilot performance, of four different visual glidepath indicator systems (the 2-bar VASI, 3-bar VASI, T-VASIS, and PAPI) in the severely reduced nighttime visual environment often referred to as the "black hole." Performance in Experiment I was best with the T-VASIS and decreased with the 3-bar BASI, PAPI, and 2-bar VASI, in that order; but differences between the T-VASIS, 3-bar VASI, and Papi were not statistically significant. Approaches flown withou the ground-vased glidepath indicators tended to be low and extremely variable. Observing behavior was compared in approaches with the T-VASIS and 2-bar VASI. Observing response frequency increased as distance from runway threshold decreased and was significantly higher with the T-VASIS. Differences in performanange provided by a given system and to the rate of observing the indicator during approaches.

Comparison of the visual perception of a runway model in pilots and nonpilots during simulated night landing approaches.

Relative motion parallax, a cue that can contribute to visual judgments of glide path angle, was studied for its effect on simulated nighttime approaches in two experiments: 1) 16 pilots and 16 nonpilots adjusted the slant of a model runway to make it appear horizontal under nighttime conditions on both dynamic trials, as the model approached them, and on static trials, with the model stationary; 2) 12 pilots and 12 nonpilots performed the same task in dynamic trials while viewing the model in a dark field as before, and while viewing the model within a window which provided a stable visual frame of reference. Neither flying experience nor the visual frame of reference enhanced sensitivity to relative motion parallax. However, some errors were smaller in pilots, indicating that flying experience enhances other runway images cues. Direct judgments of approach angle magnitude indicated overestimation by an approximate factor of 2. These findings indicate large visual illusions in the nighttime situation and suggest that the ineffectiveness of relative motion parallax may be an important part of night approach problems.

Laboratory apparatus for studying visual space perception of the pilot in simulated night approaches to landing.

The device provides a relatively inexpensive means of assessing a number of perceptual and human factors parameters in the night approach to landing situation. A technique for modeling airport runway lighting is described along with electromechanical and optical systems for precise control of simulated approach speed, model slant, and direction in the visual field of the simulated radial approach axis. The realism of this display is enhanced by preservation of the natural relations of size and brightness of simulated runway lights to distance.

Interaction between marihuana and altitude on a complex behavioral task in baboons.

Marihuana, or its principal active ingredient, delta-9-tetra-hydrocannabinal (delta9-THC), impairs performance on complex behavioral tasks in animals and man. Although there exists some evidence that altitude-induced hypoxia potentiates the physiological effects of marihuana, the interaction between altitude and marihuana on behavioral tasks has not been established. In the absence of evidence that use of marihuana is less frequent among members of the aviation community than among the general population, it was necessary to evaluate the effects on performance of any interaction between hypoxia and marihuana. Two baboons were trained to perform on a delayed matching-to-sample task at ground level and altitudes of 2438 and 3658 m (8000 and 12000 ft). The animals were orally administered doses of delta9-THC, ranging from 0.25 to 2.0 mg/kg, 2 h prior to experimental sessions at each altitude. No effects on accuracy of matching performance were observed for any of the drug doses or altitudes used. Amount of work output, as measured by number of trials completed and speed of responding, was not affected by delta9-THC at ground level but was markedly reduced by the higher drug doses at the 2438- and 3658-m altitudes. This interaction suggests that the behavioral impairment produced by marihuana can be potentiated by hypoxia.

Some behavioral effects of pesticides: The interaction of mevinphos and atropine in pigeons.

The interaction of the organophosphate mevinphos and atropine was examined in two pigeons performing in a variable interval schedule of reinforcement. When administered separately, both atropine and mevinphos produced a dose-related decrement in responding. The combined exposure to these drugs produced a performance decrement greater than that caused by exposure to each component drug alone. These findings suggest that prophylactic use of atropine may increase the detrimental behavioral effects of organophosphate exposure and that the atropine exposure alone may produce serious behavioral deficits.

The effects of mevinphos on appetitive operant behavior in the gerbil.

The need for study of the effects on performance of non-lethal organophosphate insecticide exposure is founded on many reports of behavioral difficulties in aerial applicators following exposure. In this study, a different pair of gerbils served in each of the following schedules of reinforcement: FR 25, FR 75, DRL 12-sec, DRL 20-sec, and VI 1-min. Baseline performance in these tasks tended to be comparable to that of more common laboratory species, but was more variable in the case of the VI 1-min task. Mevinphos doses of 0.20 mg/kg and above produced observable somatic signs of poisoning and also produced dose-related decrements in performance in FR and VI tasks. Performance in the DRL schedule was affected only at a dose of 0.30 mg/kg. No performance deficits or overt somatic signs of poisoning were present at mevinphos doses of 0.10 mg/kg or lower. These results do not agree with those of an earlier study which decrements in VI performance of pigeons and squirrel monkeys appeared at low mevinphos doses which did not produce overt somatic signs of poisoning. The possibility of variations in mevinphos effect as a function of species and task was discussed.