What is the definition of interlocking in railroad terminology?

In railroad terminology, interlocking refers to a complex arrangement of signal appliances and track switches that ensures trains operate safely. This system is designed such that the signals must succeed each other in a specific, correct sequence. The primary purpose of interlocking is to prevent conflicting movements and accidents by automatically controlling track switches and signals based on the positions of trains. This means that only when it's safe will the system allow a train to proceed, ensuring that the operation of the railroad is both safe and efficient.

The focus on the requirement for proper sequencing distinguishes interlocking from other railroad systems. For example, while signals and track designs are involved, the essence of interlocking lies in its sequential control of those signals in relation to the position of trains on the tracks. This aspect is what makes the choice accurate and essential for understanding how interlocking contributes to railroad safety and operation.