[Recording movement traces in field studies]

A method is presented for the simultaneous recording of body movements in space and electrophysiological data in field studies in order to obtain criteria for the evaluation of muscular and mental effort, with the aim of improving the design of workplaces--here exemplified the driver's cab of a railway engine. Eight light-emitting diodes were attached to certain parts of the body and their positions recorded by means of a video system. The positions of the diodes were computed off-line with the aid of image-processing system. In comparison with the resolution of the video camera the accuracy of determining the coordinates of a diode can clearly be improved by computing the center of its imaged bright area. In combination with recordings of the eye movements and the railway track by means of an extra video camera, evaluation of the movement traces permits a differentiated study of specific movements and actions.