Ergonomic aspects of newly designed diesel railcar types Ki-Ha 90 and 91 of Japanese National Railways are photographically, demonstrated and compared with older types of driver's cabs. Some photos were taken in case of an ergonomic study on the driver's motion and physiological reactions in the cab. These diesel railcars have main controllers with forward and backward movement which are located in both sides of the driver at proper height. This enabled appropriate layout of main dials, wide leg room and improvement of panel-desk structure. Only four main dials as a speed-meter, a clock, a pressure gauge and a voltmeter are set in the front panel with warning lights at the right of them. Attention was also paid as to wider visual field through windows, visibility of dials and signal lights, setting of Automatic Train Stop system instruments or driver's seat.

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A short review is presented of the existing knowledge on the human error effects on the performance of system: special emphasis is placed on the human reliability. In addition, the associated technical procedures and illustrations are described briefly on the use of the human error failure rates (human reliabilities), and two examples of estimations are prepared tentatively, including the design of human tasks and specific items of man operated equipment.

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Studies on human errors as psycho-physiological phenomena were reviewed and discussed. Physiological background conditions as shift of working state, fatigue, lowered physiological level or concentration of attention as well as environmental conditions play essential roles in error commission. The process how an error may be induced and thus lead to an accident should be classified into four cases: insufficient input informations, modification of input perception, lowered cortical function and improper output performance. As ergonomic measures for prevention of errors attention should be drawn to such factors as aptitude of workers, sufficient inputs and their visibility and audibility, false reading, direction of operation or the memory time and others.

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The prospect of technical measures to obtain higher reliability of man-machine-system was discussed from ergonomic viewpoints. Quantification of the human reliability is necessary and may be applicable for system designing, although more efforts should be made in this respect. Mechanization of human performances as well as ergonomic measures to guarantee good working conditions are essential. Analysis of human characteristics in task performances is still very poor as to their reliability and should be further promoted. Examples of airplane accidents, human control activity, teaching machines and others were also discussed.

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In the face of very complex industrial systems it is important to improve the system reliability. What matters is not to design a system which will never be in disorder but too expensive, but to design those machines which are reliable enough for the given environmental conditions, and to have derating or fail-safe functions for disorder cases. Human error probability should then be lowered through ergonomic measures. Quantification of human factors which are to be considered inn the system design is urgent for the optimum judgment.

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Some important analytical disciplines of the reliability of man-machine-systems were reviewed. Methodological aspects of the prediction of error probability, determination of error criticality, appreciation of functional redundancy or safety engineering techniques were introduced.

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A continuous recording technique of the systolic blood pressure during work has been developed. A blood flow detector by means of a CdS-cell applied of a finger or an ear-lobe was combined with an air compressor through an and-or-not circuit which worked to keep the air cuff pressure approximate to the systolic blood pressure. Ear-lobe application was preferred in case of motor-car drivers. A polygraphic recording during the motor-way driving revealed that the blood pressure increased by 35-40mmHg or even more at the maximum. Blood pressure level was not always parallel with heart rate variations. In critical cases of some drivers as in passing, a blood pressure level of more than 40-60mmHg higher than the resting level was observed. Personality of drivers seemed to have certain relations with blood pressure increase during driving.

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Ergonomic aspects of the design of a teaching machine system were studied. Standing operation by the teacher was considered to be preferrable. Push button switches with locking mechanism for pupils' selective responses, lamp coding as well as proper panel layout for both of the teacher's and pupils' panels and others were taken into consideration. The questions should be given by a projector from the back of the teacher, in order to ensure a bright room condition. Questionaire investigations showed that the pupils were of positive opinion for the machine teaching.

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Control of speed of automobiles on a critical curve of a national road was intended by means of planning the change effects through continuation of coloured road signs along the curve. Coloured road signs, of each 5cm spuare, headed by two safety-red signs as sensing instructions were placed with an interval of 2m and the colour was changed from white to yellow, orange and then to red. The red signs were displayed for about 50m and the colour was then returned again also gradually to yellow. The begin of those stimulations was determined so that the driver could have braked down the speed as low as 40-50km/h before the critical point approached. One year after the setting of the signs only 3.3% of cars passing the curve exceeded the safety limit of 55-60km/h, as compared with 50% before the setting, and no accidents have been reported so far. The experiment clearly demonstrates the importance of forming a short circuit in input-performance mechanism by continuous stimulations.

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