2009 – Nov – Burton – How many interlockings does it take to signal a freight train?

Noel Burton BSc MIRSE
 Westinghouse Rail Systems Australia The title of this technical paper may be a little misleading but like all good attention grabbing headlines has at least some connection with the story. The content of this paper details the re-interlocking of the Hornsby station area. As the layout at Hornsby is extremely complicated as well as compact, previously four Solid State Interlockings (SSIs) were required to control the area. To need so many of the relatively large SSI interlocking in an area small enough to be bridged by a single freight train, indicates that the original resignalling project was quite a challenge. The paper includes an overview of the original SSI implementation and the engineering journey to commission the new WESTLOCK interlocking to eventually reduce that number.