抄録
Results of an experimental study on physiological load of electric locomotive drivers with or without an assistant were analyzed. The study was conducted to offer materials to the Electric Locomotive-Diesel Locomotive Committee which was responsible to investigate whether dispensing with assistant drivers would affect the safety of trains. The purpose of the present paper is to discuss the relation of the observed variation of cortical functions to the driving load. Eight drivers drove a special train with passengers or freight between Okayama and Hiroshima in the daytime either with an assistant or by experimentally introduced single-driver plan. 1. Average heart rate significantly increased during single-driver driving, as compared with driving with as assistant. The relative increase in beats/min was 2.9 in straight sections and 4.6 in curved and slope sections. The increase was more pronounced in driving situations which demanded increased attention as on down-hill tracks or when nearing the station. 2. Distribution of intervals of saccadic eye movements proved to be a composite Weibull distribution. Percentage of rapid shift of eye movements with intervals of less than 600 msec, which might be indicative of increased caution, was found to increase significantly when advancing through station yard without an assistant. But this tendency disappeared at the latter period on the way back. 3. Factor analysis was conducted on a date matrix of the critical fusion frequency of flicker measured at total 52 sessions of two- and single-driver driving. Throughout on- and back-way of two-driver driving one and the same factor was dominant, while single-driver driving was characterized by the alternation of the dominant factors after on-way and the back-way had high weights of a factor associated with periods of declined flicker fusion levels. If eight engineers were divided into two groups according to another factor analysis on subjects by the same data matrix, there was found a group of engineers who showed a distinct decrease of the fusion frequency during the single driving. Those results may suggest the possibility of unfavourable influences of prolonged driving or insufficient rest on cortical functions by introducing the single driver plan. The conclusions of the ELDL Committee that the increased loading of drivers by the single-driver system might even enhance work capacity for safely without any increase of fatigue effects should thus be reexamined and discreet investigations under various actual duty conditions would be nesessary to meet the risk of train accidents.
