Study of Evacuation Times Based on General Accident History·

The RADTRAN 4 computer code, which calculates estimates of accident dose-risk corresponding to specified transportation scenarios, ascribes doses to potentially exposed members of the public. These persons are modeled as not being evacuated from the affected area for 24 hours following a release of radioactive material. Anecdotal evidence has suggested that this value may be unnecessarily conservative; consequently, risk estimates are unnecessarily high. An initial survey of recent trucking accidents, reported in newspapers and other periodicals (1988 through 1994), that involved evacuation ofthe general population in the affected areas was undertaken to establish the actual time required for such evacuations. Accidents involving hazardous materials other than those that are radioactive (e.g., gasoline, insecticides, other chemicals) but also requiring evacuations of nearby residents were included in the survey. However, the resultant set of sufficiently documented trucking incidents yielded rather sparse data [Mills and Neuhauser, 1995]. When the probability density distribution of the truck accident data was compared with that resulting from addition of four other (rail and fixed site) incidents, there was no statistically significant difference between them. Therefore, in order to improve the statistical significance ofthe data set, i.e., maximize the number of pertinent samples, a search for evacuations resulting from all types of accidents was performed. This resulted in many more references; a set of 48 incidents that could be adequately verified was compiled and merged with the original two data sets for a total of 66 evacuation accounts.