NSW government outlines four potential light rail routes to link Sydney's west

The NSW government has revealed its preferred destinations for a light rail network in Sydney's west.

Parramatta will be the hub but the track could head north to Castle Hill or south to Basnkton, with a stop at Olympic Park on the cards.

Four preferred routes for western Sydney's light rail have been revealed including Castle Hill via the Old Northern Road, north-east to Macquarie Park via Carlingford, Sydney Olympic Park and Strathfield or Parramatta to Bankstown in the south.

"Once we make a decision we get cracking," Transport Minister Gladys Berejiklian said.

The Carlingford plan is emerging as an early favourite which would see the existing heavy rail line converted.

"My favourite is the Carlingford line...replace the Carlingford line and Parramatta will be joined up to the university of Western Sydney," Paramatta MP Geoff Lee said.

The government is spending 400 million dollars on planning but the line will be built largely by the private sector.

Opposition Leader John Robertson said the plan lacked "substance" and called for the government to set a completion date.