What term describes an arrangement of signals, switches, and control apparatus interconnected to permit safe train movement over routes only if non-conflicting conditions exist?

• A. Automatic Block Signal System
• B. Line-Of-Sight
• C. Pocket Tracks
• D. Interlocking

Answer: (D)

Interlocking is the arrangement of signals, switches, and control equipment interconnected to ensure safe train movement over routes only if non-conflicting conditions exist. It works by locking together the signals and switch positions so that a route can be cleared only when it cannot conflict with another movement. If two possible paths would put trains on a collision course, the system prevents those paths from being set, and it won’t allow signals to indicate proceed for conflicting routes. In essence, interlocking guarantees that only non-conflicting routes can be commanded and maintained, protecting movement at junctions and hardware intersections.