What is an interlocking in railway signaling?

• A. A system that divides track into sequential blocks with occupancy detection.
• B. A safety mechanism that prevents conflicting train routes by coordinating signals and track switches so two movements cannot occupy the same path simultaneously.
• C. A device that detects track occupancy using loop detectors.
• D. A signaling system that requires manual route setting by operators.

Answer: (B)

An interlocking is a safety system that ensures signals and track switches are coordinated so two movements cannot occupy the same path at the same time. It works by strictly linking the status of signals to the position of track switches and the occupancy of routes, so a signal can only show proceed if the route is properly set and clear. This prevents conflicting signals and routes from being available simultaneously, which is the core protection against a possible collision at junctions or crossings.

This is why the option describing coordination of signals and track switches to prevent two movements from occupying the same path is the best fit. It goes beyond simply dividing track into blocks or detecting occupancy with loop detectors, and it isn’t about manual route setting—interlocking can automate safe routing by enforcing the correct relationships between signals and switches.