The government is tipped to commit to funding Auckland's City Rail Link two years early.

Prime Minister John Key is expected to announce the Government will help fund Auckland's $2.5 billion inner city rail link two years earlier than originally promised.

It's understood the PM will make the commitment in a speech to the Auckland Chamber of Commerce on January 27.

The City Rail Link will join up Auckland's train network, allowing for double the number of trains and passengers and making rail a more attractive alternative to driving on the city's congested roads.

In 2013, the government agreed it would jointly fund the CRL with Auckland Council, but said it would provide its share in 2020.

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Supplied The CRL will include two new train stations, Aotea and Karangahape Rd.



However, Auckland Council has long lobbied for a 2018 start date.

It passed its new Long Term Plan last year based on the premise that construction of the CRL would begin in 2018 and be finished by 2022. Enabling works for the project are already underway.

If Key confirms funding in 2018, it means the council can meet that target.

The CRL will provide a rail loop through downtown Auckland, allowing trains to go in both directions.

The government has always said it would consider an earlier start if rail patronage and employment growth in the Auckland CBD hit certain targets.

Patronage of Auckland's rail network grew by 22 per cent in 2015.

The CRL will link Britomart station in downtown Auckland with the existing western line at Mt Eden station, allowing trains to run both ways through Britomart.

At the moment the station is a dead end, severely constraining future growth on the rail network.

"Any statement providing certainty over government funding of the City Rail Link and an early start to that funding would be welcomed by Aucklanders," said Mayor Len Brown.

He has been working closely with Prime Minister John Key, Finance Minister Bill English and Transport Minister Simon Bridges with regard to the urgent need for the CRL.

"At current growth rates, the patronage target set by the government for funding the CRL will be achieved by the end of the year, three years ahead of schedule."

The government's target is 20 million rail trips a year. There are already more than 15 million trips a year.

Preliminary work on the CRL started last month.

Auckland Chamber of Commerce chief executive Michael Barnett confirmed Key would address its membership on the issue of infrastructure funding for the city.

It would be similar to his announcement in 2013 in that he would outline the government's future commitment to the city "and I think give some clarity and certainty to some of the investment in infrastructure that needs to be made".

Asked if that would include a statement on the timing of the CRL funding, Barnett replied: "If they put a stake in the ground and then there's clarity, then everyone can work around that."

The Chamber of Commerce supported a 2018 start for the rail project, he said.

Transport blogger Patrick Reynolds said he understood the government would stump up with the funds earlier than 2020.

It would be fantastic news for Auckland, but it would also be interesting to hear what else Key announced, he said.

"It not only matters what you do build, it also matters what you don't build," he said.

Auckland grew by the entire population of Wanganui last year, and it could do that every year for a long time to come, he said.

He was concerned that the National government would also announce more "sprawl subsidies" such as additional funding for motorways.

Auckland needed to be an intensified, dynamic urban centre which could compete with the Australian cities, Reynolds said.

A spokesperson for John Key said his office could not disclose the content of the PM's speech this far out as it was still being confirmed.



WHAT YOU NEED TO KNOW

What is the City Rail Link (CRL)?

The CRL is a 3.4km underground train line which will run from Britomart station in downtown Auckland through the CBD to connect with the existing western line at Mt Eden station. It will include two new train stations – Aotea, near Aotea Square, and Karangahape Road in Beresford Square, just off K Rd.

When will it be built?

The CRL will take five-and-a-half years to build. Work on installing a new stormwater pipe in Albert St to make way for it began in December 2015. Enabling works for the project – a pair of cut-and-cover tunnels up Albert St to Wyndham St – will start in May 2016. At this stage, Auckland Council says the main chunk of work will begin in 2018, meaning the project would be finished by 2022. But it has been at odds with the government which has said it would not provide its part of the funding until 2020.

How much will it cost?

It's estimated the CRL will cost $2.5 billion to build. Most of it is being jointly funded by Auckland Council and the government, although the details of who is providing what and when have yet to be worked out. The council has also done at least one deal with a private company, Precinct Properties, which will build the stretch of tunnels underneath the Downtown shopping centre as part of its upcoming redevelopment of the site.

Why does Auckland need a CRL?

In the past decade patronage of Auckland's trains has grown from 2.2 million trips a year to 15 million. But further growth is constrained because Britomart station is a dead-end, limiting the entire rail network's capacity. The CRL will join up the network, allowing trains to run both ways through Britomart. This will double the number of trains that can run, and carry 30,000 people an hour at peak times. Without the CRL, the network stays limited to a maximum 15,000 people an hour.