Is commuter rail the best way to ease congestion in Christchurch city?

A commuter rail service to ease traffic congestion in Christchurch's north is back on the city council's agenda.

Christchurch City Council has decided to again look into using the existing rail network, despite an Environment Canterbury (ECan) investigation last year ruling out this option as a temporary solution to traffic woes because of its $10 million price tag.

Cr Ali Jones said she had spoken to numerous people who believed the costs quoted in the ECan report were "hugely inflated".

The council last week decided to initiate a business case process for a future public transport study with its strategic partners including NZ Transport Agency (NZTA), ECan and the Selwyn and Waimakariri district councils. This would include looking at rail and bus transportation across the city.

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Christchurch Mayor Lianne Dalziel said she did not want to raise expectations that the city could afford to investigate a rail option on its own, because it could not.

"The cost of even considering this option and doing it alone is massive," she said.

"You can say the solution is staring us in the face. It's not just a straightforward 'yes we can just throw some trains that we don't have, on to a track that we don't have access to'. It sounds simple. I'm just saying it's not."

Dalziel asked where people would go once they got off the train in the city because additional infrastructure and services would need to be provided, which would cost a lot of money.

Jones said those issues would be included in any business case or study.

Council staff will now come back to councillors with advice on using the existing rail infrastructure.

The rail discussion was sparked by the Shirley-Papanui Community Board, which has been pushing for the council to prioritise rail to resolve traffic congestion in the north.

Board chairman Mike Davidson said the opportunity to build "a good light rail system" in Christchurch was slipping away, but he did not believe it was too late.

The council needed to look at a short to medium term solution and the rail tracks were "staring us in the face", he said.

"To relieve the pressures, that is an option that needs to be considered strongly."

Council's transport and research unit manager Richard Osborne said if the council did not engage with NZTA from the beginning, it would not get funding, and it also needed ECan and Waimakariri and Selwyn district councils in the room.

"If we don't bring them in from the beginning, the success of this work would be diminished and we'd end up with something not useful," he said.

Osborne believed the business case needed to encompass all of Christchurch and not just focus on rail, but look at a number of rapid transport options, including bus.

Cr Phil Clearwater agreed, saying the city needed to consider rail as part of a wider public transport network and it was "madness" to look at rail in isolation because the issue was far too important.

Jones was concerned a wider Christchurch approach looking at other options would dilute the focus away from the northern entrance of the city.