It was formed to deliver commitments made by the McGowan Government during the 2017 election campaign.

The extensions were to be arranged into two "circle routes": a North Circle that would share parts of the Joondalup line (from Perth to a new station at Balcatta), Ellenbrook line (from Perth to Noranda), and Wanneroo line (from Noranda to a station at Alexander Drive), along with exclusive tracks and stations between Alexander Drive and Balcatta; and a South Circle that would share infrastructure with the Airport line (from Perth to Forrestfield), the Thornlie line (from Thornlie to South Lake), and the Fremantle line (from Fremantle to Perth), with exclusive tracks between Forrestfield and Thornlie, and between South Lake and Fremantle.

[5] While unsuccessful in winning government,[6] the re-elected Barnett Ministry formally approved an alternative airport link in 2014.

[8] That was expanded to reincorporate a rail line to Ellenbrook and Karnup station by December 2016.

[9] After the election of the McGowan Government, the Metronet multi-agency team was formed in 2017 to deliver the commitments.