The purpose of this study is to investigate the mehtod of estimating navigators' work-load by the autonomic nervous activities which are given by the spectral analysis on the changes of heart beat interval (R-R interval). Experimental ships manoeuvring tasks in the simulator, which were on fairway with other vessels, were performed by four subjects that were 3 captains and a chief officer. We recorded a R-R interval during the tasks and analyzed the changes of the records every for 5 minutes by means of Coarse-graining spectral analysis (CGSA method). We accumulated power spectrum of three frequency bands; Lo=0〜0.15Hz, Hi=0.15〜0.8Hz, total=0Hz〜, Lo/Hi and Hi/Total were calculated to evaluate sympathetic (SNS) and parasympathetic (PNS) nervous activities. The SNS activities increased and the PNS activities decreased when there were vessels which were crossing or nearing. On the contrary, when those vessels didn't exist, the SNS activities decreased and the PNS activities increased. We calculated the average number of other vessels that crossed or closed to their vessel every for 5 minutes to evaluate the marine traffic environment. It was not recognized that the correlation between the average and heart rate. However, there was the positive correlation between the average and the SNS. These results suggest that the method of estimating by autonomic nervous activity by CGSA on heart beat interval changes is a useful to evaluate navigators' work-load.
