(a) An emergency/disaster is damage to an IRR transportation facility that:

(1) Renders the facility impassable or unusable; and

(2) Is caused by either a natural disaster over a widespread area or catastrophic failure from an external cause.

(b) Some examples of natural disasters are: floods, droughts, earthquakes, tornadoes, landslides, avalanches, and severe storms.

(c) An example of a catastrophic failure is the collapse of a highway bridge after being struck by a barge, truck, or landslide.