Abstract
This investigation was conducted to examine the climatological features of disasters by low visibility with dense fog occurred from 1971 to 1997 in Japan. Most of the damages in the disasters were traffic hindrance or traffic accident. The data for unusual weather and meteorological disasters, which were compiled by Japan Meteorological Agency, were used in this study. It is estimated that they include about half of the disasters with human damage but include only small part of traffic hindrance with only light loss. Traffic accidents with human damage do not happen so often on land but quite often for marine cases. For land cases, they may be increasing because of extending faster traffic systems, especially highway network. The climatological features of the disasters have discrepancy with the features of the fog appearance by routine meteorological observations. The difference in intensity or spatial distribution pattern of fog might causes this discrepancy. The fog associated with advection of warm air, extratropical cyclone, front, and precipitation system often affect to human activities in Japan.

【キーワード】：濃霧，視程不良害，交通障害，交通事故，災害統計
【Key words】： dense fog, disaster by low visibility, traffic hindrance, traffic accident, disaster statistics

*気象研究所
Meteorological Research Institute