Abstract
　The heavy rain which swept over Nagasaki district on July 23, l982, killed 299 persons and damaged so seriouly to Nagasaki city and its vicinity. Roads of Nagasaki city were submerged by flush flood. Many cars were washed away by flood and let along anywhere, so about 20 car drivers were killed. On the other hand, the damage of buses were not so serious and it is considered that buses are a safe transportation system when it rains heavily. However, many buses which were running were cancelled everywhere. Buses were isolated from the outside as well as owner driver's cars. Therefore, bus drivers were very busy because they must collect informations about roads and disaster, make contact with the operation center and order passengers to get off for evacuation. It seems important problems for traffic disaster prevention are presented. In the present work, bus disaster is investigated by interviews and questionnaire for bus drivers. Damage for buses due to flood and driver behavior are clarified and prevention for traffic disaster by flood is shown.

*長崎大学工学部
Faculty of Engineering, Nagasaki University