Tunnel fit-out and track laying

Tunnel fit-out is an essential part of the project and includes installation of rail infrastructure and electrical, mechanical, hydraulic, safety and communications systems.

View an illustration of the tunnel fit-out components.

Early fit-out of the tunnels and preparation works for rail began mid-2019. The tunnel boring machines completed their work in April 2020, paving the way for track laying and other fit-out works.

For rail within the tunnels, a fixed track slab method was used, with rail fastening systems affixed to embedded sleepers and infill concrete.

The construction was completed in three stages:

  • Installation of rail and sleepers
  • Setting the track to line and level
  • Concrete placement and finishing

Track located outside the tunnels and dive structures is placed on a bed of crushed stones, referred to as ballast. The ballast supports the sleepers and rail, keeping them in place while trains run. Ballast also assists with water drainage.

The first length of above-ground track – including the first turnout – was placed at Bayswater Junction in October 2020. It is here where the Midland and Airport Line tracks will merge before trains arrive at Bayswater Station. Track laying was completed in July 2021.

Watch a video about the start of track laying within the tunnels or view the tunnel fit-out and track laying fact sheet.


Tunnel rail tracker

Includes dive structures. Track laying is complete,

Tunnel One Tunnel Two Total

Skeleton track (rail strings clipped onto sleepers)


8350m 16,720m

Slab track (skeleton track embedded in concrete)

8370m 8350m




The total length of rail strings


The number of sleepers used within the tunnels


of Australian-made track steel used