What is defined as a Derail in MTA terminology?

In MTA terminology, a derail is specifically defined as a permanent device that is non-interlocked and affixed to the rail. This device is designed to prevent trains from inadvertently moving onto a track that is out of service or is not intended for trains. The primary function of a derail is to safely guide the wheels of a train off the tracks in a controlled manner, preventing potential accidents or derailments if the train were to approach a hazardous area.

The characteristics of a derail, as a permanent device, distinguish it from other forms of track safety equipment. While temporary devices or signals may assist in directing train movements, the derail's role is focused on physical prevention rather than signaling or switching. Its fixed nature contributes to ongoing safety on the rail network, ensuring a level of reliability in protecting both the infrastructure and the operations of train services.