Track segment-specific accident rates are determined based on the
inferred FRA track classes and corresponding accident rates (21).
The length of the track segments was determined from the GIS data.
It was assumed that all tank cars used were DOT 105J300W pressure
cars with a steel jacket, insulation, full-height head shields, and a tank
thickness of 0.6875 in. These cars have a conditional probability of
release of 0.0691, given that they are derailed in a FRA-reportable
mainline accident