
thumb|upright|Hinged derail with automatic blue flag
thumb|upright|Hinged derail with automatic blue flag
A derail or derailer is a device used to prevent fouling (blocking or compromising) of a rail track (or collision with anything present on the track, such as a person, or a train) by unauthorized movements of trains or unattended rolling stock. The device works by derailing the equipment as it rolls over or through it.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).