"Wheel off track" is a derailment. Doesn't have to mean a huge wreck and pile-up. Can happen at low speeds. The vast majority aren't that big a deal. (my dad e

"Wheel off track" is a derailment. Doesn't have to mean a huge wreck and pile-up. Can happen at low speeds. The vast majority aren't that big a deal. (my dad ended his career in middle-management with a railroad—not Norfolk, but for all I know Norfolk owns the one he worked for now, there was a lot of consolidation—and for a few years he had to travel to derailments in his region, when they happened, and derailments happened somewhat often)