[5] Planning for the original North West Rail Link which later became known as Sydney Metro Northwest was a long and complex affair.

The following proposals were endorsed at one time or another by the government: By May 2015, media releases from Transport for NSW used the name "North West Rail Link" to address the whole section between Rouse Hill and Chatswood and not just the unbuilt part.

[19] At least 150 boreholes with a diameter of up to 15 centimetres (5.9 in) will be drilled up to 75 metres (246 ft) deep along the proposed alignment between Epping and Rouse Hill in order to develop an understanding of the geological profile.

In June 2013, the Tunnels and Station Caverns (TSC) contract was awarded to a joint venture involving Thiess and John Holland, and Dragados.

[23] In December 2013, the Surface and Viaduct Civils (SVC) construction contract was awarded to a joint venture between Italian firms Impregilo and Salini.

[33][34] Previously, there were long-term plans to extend the proposed heavy-rail North West Rail Link to meet the existing Richmond railway line near Vineyard.

[36] A Transport Department report dated 9 June 2011 shed more light on such plans, suggesting an extension of the North West Rail Link beyond Rouse Hill to meet the Richmond line at Schofields, Riverstone, or beyond.

The viaduct and ground level section between Tallawong and Bella Vista uses standard overhead wires to supply power.

For the rest of the line (formerly part of the Epping to Chatswood rail link [ECRL]), the existing sagged catenary overhead wires were retained, with an additional copper cable added in some sections due to the increased current draw of the new rolling stock.

[43] This led to a deadlock between the State Government and Baulkham Hills Shire Council regarding construction of the $200 million Mungerie Park industrial and residential development at Kellyville.

On 5 June 2000 the Council voted to defer planning approval for the Mungerie Park development until the State Government demonstrated a commitment to improve local transport infrastructure, which included building the North West rail link.

[44] Member for the then-State electorate of The Hills, Michael Richardson, submitted a Freedom of Information request for the draft report on 3 November 2000.

[45] The State Government formally rejected the Freedom of Information request on 9 January 2001, despite acknowledging that release of the report would be in the public interest.

[48] The Action for Transport 2010 cost blowout was seen as the reason for the State Government's refusal to release the draft report into the North West rail link route.

[51] A 2002 NSW Treasury report mentioned the North West rail link, and that it was "under development or investigation", but no estimate of cost or start date were provided.

On 3 October 2002, the Minister announced a feasibility study for an extension of the proposed route beyond Rouse Hill to meet the existing Richmond Line.

[54] Various studies in support of the Epping to Castle Hill link were made during 2003; most of this work related to the proposed alignment of the route.

[57] On 9 June 2005, the State Government announced the Metropolitan Rail Expansion Program (MREP), an $8 billion plan to add three new railway lines to the CityRail network over the following 15 years.

In April 2006, the NSW Transport Infrastructure Development Corporation released the North West Rail Link Project Application and Preliminary Environmental Assessment in support of the planning approval process.

The inability of Iemma to privatise the state-owned electricity sector to fund the metro project culminated in his resignation as NSW premier in September 2008, and the appointment of Nathan Rees as his successor.

Then, on 31 October 2008, the NSW Government announced that the North West Metro would be indefinitely deferred due to budgetary cuts.

[63] On 21 February 2010, two and a half months after Kristina Keneally had become Premier, the NSW Government revealed the cancellation of the Sydney Metro project in its Metropolitan Transport Plan[64][65] and returned to the North West Rail Link proposal.

[66] On 6 April 2011, Premier O'Farrell and newly installed Transport Minister Gladys Berejiklian announced the project team that would be responsible for construction and delivery of the North West Rail Link.

[71] The design was changed to a driverless rapid transit line, featuring more frequent, lower capacity single deck trains.

[28][36] The proposed stations were: On 15 May 2011, Transport Minister Gladys Berejiklian announced that a tender had been called for engineering, rail systems and architecture services.

[76] The tender documents indicate the Government's desire to appoint a financial adviser to examine the possibility of securing funding from private sources.

[29][68][78] Applications for the first six of twelve tenders closed the week of 8 July 2011 with 44 proposals having been received from a range of Australian and international companies.

[79] As part of the tender process, applicants were asked to demonstrate how they would design station precincts at the Rouse Hill, Samantha Riley Drive and Cudgegong Road sites.

[81][82][83][84] The consortium were tasked with investigating route alignment options, rail systems, tunnel design, station locations and infrastructure planning.

[94] Results of a cost-benefit analysis released in November 2011 indicated that the North West Rail Link would be three times more beneficial to New South Wales than the Parramatta to Epping extension.