NSW Transport Minister Andrew Constance says a final decision on a rail link to Sydney's planned new airport at Badgerys Creek is "many years off", and urged the federal government to consider the large cost of such transport infrastructure.
While extending the $1.8 billion South West Rail Link from Leppington to Badgerys Creek is regarded as the simplest and cheapest option, Mr Constance said "some very significant homework" about the best choice for a rail connection had yet to be completed.
"I know Canberra is keen to see a rail line up and running from day one [of the airport opening in 2026]," Mr Constance said on Monday.
"But I would say to Canberra, if you're going to invest in an airport, you also have to look at the costs associated with the infrastructure around it, particularly to my good friend the Deputy Prime Minister, Barnaby Joyce."
And in highlighting his own government's multibillion-dollar investment in new metro train and light rail lines in Sydney, Mr Constance said he was "very interested to see what Canberra has to say in relation to investments in rail around the airport".
Prime Minister Malcolm Turnbull has said his goal is to have a rail link to Western Sydney Airport when it opens in 2026, or shortly thereafter. However, his government has yet to commit to funding a connection.
An options paper prepared by the state and federal governments last year canvassed a range of proposals for how to service the new airport, including a direct express service from Sydney's CBD via Parramatta.
While a 160 kilometre-an-hour express service could whisk passengers between the airport and the central city in less than 30 minutes, this would be one of the most expensive options because it would require tunnels for much of the way.
A price tag was not put on any of the options but the paper suggested the most expensive could top $25 billion.
In an attempt to cope with surging demand, the state government announced plans for an extra 20 express trains a week during peak hour from Campbelltown and Macarthur in the south west to Sydney's CBD on the T2 Airport Line late this year.
All T5 Cumberland and T2 South Line services will also start and end at Leppington on the South West Rail Link – Sydney's newest train line – giving commuters from the fast-growing area direct services to Parramatta and Blacktown.
However, those travelling on the T2 South Line from Campbelltown to Parramatta will need to change trains at Glenfield.
"You can't be all things to all people on a rail network," Mr Constance said.
"What we are trying to do is make sure that we make vast improvements for as many people as possible. For 80 per cent of commuters who travel into the CBD every day in the morning peak, this is a big win in terms of more services."
The government is forecasting rail patronage in Sydney to surge by 21 per cent over the next two years. Last year, patronage rose by about 10 per cent.
In December, the government awarded a $1.7 billion contract for the purchase and maintenance of 24 new Waratah double-deckers. The first of the new trains will begin running on Sydney's rail network next year.
Sydney Trains chief executive Howard Collins described as unprecedented the growth in demand for rail services, and he said "we need to match that with supply".
In a sign of the growth in Sydney's south west, the 850-space car park at Leppington station was almost full on Monday morning, just two years after it opened. And it is illustrative of the challenges facing tens of thousands of commuters each week day across Sydney as they rush to search for car parks at trains stations.
