Editing Interlocking (section)

{{short description|Arrangement of railway signal apparatus}}
{{for multi|use of the term in music|Hocket|use in electronics and computing|Interlock (engineering)}}

[[File:Des Plaines interlocking tower.jpg|thumb|The tower and tracks at Deval interlocking, [[Des Plaines, Illinois]], in 1993]]
In [[railway signalling]], an '''interlocking''' is an arrangement of signal apparatus that prevents conflicting movements through an arrangement of tracks such as [[junction (rail)|junction]]s or crossings. In North America, a set of signalling appliances and [[Track (rail transport)|tracks]] interlocked together are sometimes collectively referred to as an ''interlocking plant'' or just as an ''interlocking''. An interlocking system is designed so that it is impossible to display a signal to proceed unless the route to be used is proven safe.

Interlocking is a safety measure designed to prevent signals and [[Railroad switch|points/switches]] from being changed in an improper sequence. For example, interlocking would prevent a signal from being changed to indicate a diverging route, unless the corresponding points/switches had been changed first. In North America, the official railroad definition of interlocking is: "''An arrangement of signals and signal appliances so interconnected that their movements must succeed each other in proper sequence''".<ref>{{cite book|title=Rights of Trains|last1=Josserand |first1=Peter|last2=Forman|first2=Harry Willard|date=1957|edition=5th|publisher=[[Simmons-Boardman Publishing Corporation]]|location=New York|page=5|oclc=221677266}} Definitions.</ref>