NYC Subway Signals: A Complete Guide

The New York City subway system uses wayside color-light block signalling, a technology unchanged since 1904, which divides tracks into sections and uses trackside signals with colored lights to detect trains and maintain safe spacing between them. Tracks are divided into electrically-controlled blocks by insulated rail joints, with each signal governing a "control length" of multiple blocks to ensure trains remain separated and can safely stop if they fail to obey a red signal. While newer in-cab and radio-based signalling technologies are being gradually deployed, nearly all current subway routes still rely on this classic block signalling system coordinated by interlocking controls.