Middlemount Balloon Loop

Client: Middlemount Early Rail Alliance (GHD and John Holland Group)
Duration of works: 2010 - 2012
Location: Middlemount, Queensland, Australia


  • Delivered signalling circuits, data design, principles testing, and onsite testing and commissioning for a new 17 kilometre balloon loop track.
  • Signalling works included two new Microlok interlockings contained within two standard Queensland Rail (Aurizon) style Signalling Equipment Rooms (SER).
  • Upgraded an axle counter block to the newer Siemens counter, and modified another to an ML track circuit block.

The key challenges of the project were:

Due to the reduced length of the Middlemount Junction to Bundoora block, a distant signal was unable to be positioned at braking from the signal protecting the junction. This required starter signals to be upgraded to have a Yellow aspect, with the interfacing and aspect sequencing fed via a copper cable from a new SER. Dual telemetry links were designed into the SER, with a single telemetry link designed into a second new SER using fibre.