FRA train accidents (U.S. & Canada) are defined as:

Any collision, derailment, fire, explosion, act of God, or other event involving the operation of on-track equipment (standing or moving) that results in total damages to all railroads involved in the event that is greater than the current reporting threshold (year 2015 $10,500 US or $13,900 CDN) to railroad on-track equipment, signals, track, track structures, and roadbed.

Source: FRA Guide for Preparing Accident / Incident Reports - Office of Safety. May 1, 2003 - DOT/FRA/RRS-22