Human Factors: The Journal of the Human Factors and Ergonomics Society

Data are examined from two published experimental studies in which drivers were instructed to drive other than normally, with the traffic: for example, to minimize fuel consumption or to minimize trip time. It is found that, in general, for each 1% increase (decrease) in trip time compared to driving normally with the traffic, the fuel consumption increases (decreases) by approximately 1.1%. However, expert drivers can save fuel without increasing trip time by skillfully adjusting their speed to avoid stops at traffic signals. It is shown that the formal problem to be solved to minimize fuel consumption on an urban trip is so complicated that even a “perfect” fuel economy meter would not enable a driver to achieve this minimum.

Factors affecting the productivity of intellectually challenged office workers have not been systematically investigated. The impact of environment (lighting, noise, pleasant sounds, landscape, etc.) on the expressed productivity of 11 office workers engaged in decisionmaking, design, and/or creative work was explored in a realistic office setting. A novel feature in the experimental office environment was an “artificial window,” designed as a substitute for an outside window in an interior office, using motion picture loops of outdoor/nature scenes projected onto a back-projection screen. Matching nature sound or music could also be introduced as accompaniment. For long-term comfort and productivity, the artificial window was rated nearly as desirable as an outside window. Additional findings were that subjects preferred low-level music or nature sounds to a totally quiet office, and that introduction of these sounds could also block to some extent the undesirable effects of cyclic-pattern industrial noise. However, the introduction of music or nature sounds in concert with random-pattern noise, such as in a very noisy office, tended to accentuate the undesirable effects of the noise.

An attempt was made to provide direct, quantitative assessment of environmental and equipment variables on diver work performance. Five male volunteer divers were each given 12 training trials on a standardized, U. S. Navy work task before exposure to eight, randomly presented, experimental visual and tactile conditions. A two-factor repeated measures design was utilized with four levels of luminance degradation and two levels of tactile restriction. Divers were required to perform standardized work underwater while measures of heart rate, errors, and time to complete the task were taken. Results indicated that significant changes occur in measures of time to complete the task and errors, as a direct function of tactile and luminance degradation.

Pulmonary ventilation ( _E) and oxygen uptake ( _O2) were measured and regressions between them were found for men and for women exercising from light levels (1.3 kcal/min) to maximal levels (20 kcal/min) of work. Increases in pulmonary ventilation were proportionately greater than increases in oxygen consumption, and, therefore, nonlinear regressions were determined for a range of _E which was wider than the linear regressions previously suggested by other investigators. Because the data for men and women diverged, two separate curves were computed. In addition to the sex differences, each equation had an adjustment for age. The standard error of estimate for _O2 was 0.21/min.

Two laboratory experiments were conducted to assess the usefulness of visual acuity as a personnel selection criterion. In the first experiment a screening technique (fractional factorial) was employed to determine the relative effects of eleven factors on target acquisition performance. The factors and first-order interactions were ranked by the percent of the variance in the data for which each accounted. Slant range, far visual acuity, masking, and target type were among the highest ranked factors. Search times and detection probabilities were measured in the second experiment as far visual acuity, slant range to the target, masking, and observer experience were varied in a full factorial design. Masking accounted for most of the variation in the data followed by slant range and visual acuity.

Performance on two auditory choice reaction time (RT) tasks was studied in a group of 12 subjects under the influence of graded doses of ethyl alcohol ranging from placebo to 1 g/kg body weight. Deadline procedures were employed in a side discrimination and a pitch discrimination task to permit the calculation of speed-accuracy tradeoff functions (accuracy versus RT). Accuracy declined as a function of dose, but alcohol did not significantly influence RT. Conversely, accuracy was not affected by task; but the pitch discrimination task required an average of 88 ms more time than the side task. Alcohol dose and task produced independent effects on the speed-accuracy tradeoff function. As dose increased, the slope of the tradeoff function declined; but slopes were equivalent for the two tasks. On the other hand, the x-intercept (where accuracy equals chance levels) was 90 ms greater for the pitch task than for the side task.

Eight different configurations and color combinations of rotating-beam emergency vehicle lights were evaluated in terms of information conveyed about rate and direction of travel when viewed at night. The lights were viewed moving toward or away from stationary observers at rates of 0, 5, and 10 m/s at overall ranges of 300 to 450 m.

Differences were found between individual lights in terms of illusions of motion, signal-to-noise ratios, and overall error scores. All-red lights conveyed more information than combinations of red and blue lenses in the same light. Twin lights were superior to single beacons, and twin models with a sequential mirror-generated flash pattern were superior to plain ones.

Several of the lights created an illusion of receding motion when actually at rest. This was most severe for a side-to-side alternate flash pattern using red signals. Lights considered to be highly conspicuous were not necessarily those with the best information transfer characteristics. The cues relevant to this perceptual task appeared to be provided by changes in light intensity with distance, rather than changes in angular displacement.

This research evaluated the sensitivity of four observer response measures to variations in the character size and dot luminance of a dot matrix display. Specifically, the research determined the sensitivity of recognition accuracy, response time, tachistoscopic recognition accuracy, and threshold visibility. Alphanumeric characters were presented to six subjects in noncontextual form on a variable-parameter CRT display programmed and driven by a minicomputer.

Recognition accuracy (percent correct response) was found to be the response measure that is most sensitive to the display parameters of character size and dot luminance. Character size, dot luminance, and viewing distance proved to have consistent and significant effects at viewing distances greater than 1.52 m. At lesser viewing distances, these parameters had little effect.

The results suggest that there is no major difference between the display requirements for computer-generated dot matrix displays versus those for conventional CRT displays.

A large amount of information on the body size of United States Army personnel, both men and women, has been collected during several anthropometric surveys carried out between 1946 and 1977. Changes in the body site of Army men between 1946 and 1966 and of Army women between 1946 and 1977 may be examined in an analysis of these anthropometric data. The data also may be utilized to define the contrasts in body size between Army men and women for application in the design and sizing of clothing and in the human engineering of equipment and materiel intended for use by both Army men and women.

The recent increase in the incidence of shiftwork has been accompanied by a change in the type of task typically performed by the shiftworker. The technological advances which have produced both these effects have meant that the shiftworker is more likely to be engaged in cognitive, mentally taxing tasks than the predominantly perceptual-motor ones typical of earlier times. Contemporary research on time of day effects in performance efficiency has indicated that these task changes may be crucially important in determining on-shift performance, and hence the choice of the individual and shift system that is most suitable. Evidence is reviewed on task demands, the effects of different shift systems, and the role of individual differences. A descriptive model is proposed in which on-shift performance is seen to be dependent on the type of task, type of shift system, and type of person, with the three factors interacting via the worker's various circadian rhythms.

Flight simulator motion has been demonstrated to affect performance in the simulator, but recent transfer of training studies have failed to demonstrate an effect upon in-flight performance. However, these transfer studies examined the effects of motion in experimental designs that did not permit a dependency relationship to be established between the characteristics of the motion simulated and the training objectives or the performance measured. Another investigator has suggested that motion cues which occur in flight can be dichotomized as maneuver and disturbance cues, i.e., as resulting from pilot control action or from external forces. This paper examines each type cue and relates it analytically to training requirements. The need to establish such relationships in simulator design is emphasized. Future transfer studies should examine specific training objectives that can be expected to be effected by motion.

The impact of metrication of roadside speed signs upon vehicle speeds was investigated for four different road types using concealed roadside radar. The study was conducted one year after metrication to determine whether there were any long-term changes in traffic patterns in addition to the short-term influences reported previously. There was no evidence for any tendency for drivers to increase traveled speed on roads for which metrication resulted in an increase in the speed limit. Analysis of accident statistics for the month following metrication revealed no significant increase in accident rate over that projected from nine-year accident trends. It is concluded that highway metrication does not present the safety hazard suggested by critics of the metrication program.