"This report describes the second of two studies of vigilance in connection with a road test sponsored by the American Association of State Highway Officials and administered by the Highway Research Board of the National Academy of Sciences. Army drivers operated trucks over experimental highways (Nov 1958 to Nov 1960) under conditions conducive to boredom and fatigue -- characteristic of many Army monitoring jobs. The primary objective of this study was to determine which, if any, of several well-known psychological domains hold most promise for prediction of vigilance performance. A total of 39 predictor and 2 reference measures, grouped into 8 predictor clusters and a single reference cluster, were administered. In general, both reliability and validity coefficients were low. The most promising predictors were the Personality, Personal History, Driver Aptitude, and Perceptual Speed clusters. The Cognitive, Physical, Psychomotor, and Attitudinal clusters were least promising. In spite of large and fairly stable individual differences in detection performance, the highly specific nature of the criterion and possible subject-task interaction appears to restrict the utility of standard general psychological predictors. Measures paralleling more closely parameters of the criterion task -- signal rates, intersignal intervals, sensory modes -- might be expected to show greater promise."--Abstract.