In 2011, the Great East Japan Earthquake and Tsunami destroyed three prefectural hospitals in Iwate Prefecture, Japan. The author interviewed officers working in the Iwate Medical Central Office as well as medical doctors working in public hospitals, of which there are 25 in Iwate Prefecture. Based on the interviews and several reports this paper describes the problem of patient transport in a large-scale disaster. In such situations, the decision making process is confusing, making it difficult to transport patients efficiently from hospitals in the disaster areas to supporting hospitals. This paper proposes a new decision making method to solve the problem of patient transport. The simulation results of a risk analysis comparing the proposed method with conventional methods are presented.