2003 年 34 巻 3 号 p. 17-29
The 2000 eruption of Mt. Usu, began following twenty three yeas of the inactive period, not only seriously damaged the surrounding area but also had a profound effect on socioeconomic activity in the entire Hokkaido region due to the disconnecting of the main transportation route linking to Japan's main island. As for the road network, the eruption cut off traffic on the “Douou” highway and Route 230 running through the Usu area and led to requiring access control along several roadways. Forcing road users to substantial detour resulted in a great loss due to increasing travel time. Additionally, depending on the degree of the increasing of travel time caused by limited access, it might make some road users to cancel their trips.
This disaster impact study is an attempt to develop a model showing travel pattern at the time of natural disaster, considering quantification of road users' cost subject to road network during the disaster time. This model can involve the situation in which road users cancel their trips as a result of increasing travel time. Therefore, it makes possible to estimate travel cost generated by impassable roadways and opportunity cost generated by trip cancellation at the same time. This is the most distinguish feature of this model. Reproducing a scenario of the limited road network at the time of the 2000 eruption of Mt. Usu with this model, the study compares the traffic census data and the assigned traffic volume estimated by this model. Furthermore, the study calculates travel time/cost and opportunity cost due to trip cancelled.
As a result of comparing actual values and the estimated values for both usual-time and disaster-time at the major points in the Usu area, we find, with a correlation coefficient of approximately 0.9, the proportion with an error between actual and estimated values for each time study is within 20%. Therefore, we can extract conclusion that the developed model shows reproducibility. Moreover, the study estimates that the total loss caused by limited road network at the time of the 2000 eruption of Mt. Usu is 47 million per day: loss as a result of travel time/cost and of opportunity cost is 22 million per day and 25 million per day respectively.