Citation

Dobbins DA, Tiedemann JG, Skordahl DM. Highw. Res. Board bull. 1962; 330: 1-8.

Copyright

(Copyright © 1962, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

Signal detection performance was studied under realistic field conditions. Vigilance is defined as the prolonged ability to detect certain environmental signals. For the road test, army drivers were required to drive trucks on experimental highways under monotonous and fatiguing conditions, thus providing a natural laboratory for a study of vigilance. The specific objectives of the human factors portion of the aasho investigation were to: (1) develop an apparatus test to measure vigilance during the actual driving process, (2) analyze the vigilance performance of a group of drivers during a one full 7-hour driving shift to determine the level of and trends in performance in detecting signals as a function of time spent in monitoring, and (3) determine the extent of individual driver differences in signal detection performance and to estimate the reliability of these differences. A portable apparatus, the u. S. Army transportation corps vigilance tester, was designed for use on the trucks. The apparatus consisted of a visual signal display unit mounted on the truck dashboard, a footoperated response pedal, and a combined programer and response recorder unit mounted on the truckbed. Before beginning a driving shift, drivers were told that lights of 1-sec duration would appear, one at a time, in different red and white panels of the display. Their test was to monitor the display unit while driving the truck and to respond only to light signals appearing in red panels by depressing the foot pedal. In spite of inhibitory factors present in this study which would lead to a prediction of performance decrement (noise, vibration, long hours, bordom and fatigue) other compensatory factors also present may have combined to cause prolonged high detection levels. The influence of inhibitory factors was apparent in increases of invariabilility of performance, rather than in levels of performance. Possible compensatory factors discussed were signal characteristics, task characteristics and subject characteristics, including motivation. The present study showed that detection performance began at a high level and stayed at a high level in spite of noxious monitoring conditions. It is suggested that the rapid, severe decrement found in the passive monitoring of laboratory displays may be of limited generality. The classical decrement curve may represent a basic and significant perceptual phenomenon under conditions of reduced organismic stimulation.