(Bloomberg) -- New Zealand’s government is seeking feedback on proposals for a second crossing for Auckland’s Waitemata Harbour to solve growing traffic congestion problems.

Officials have developed five scenarios including bridge and tunnel options, Transport Minister Michael Wood said on Thursday. A decision on the preferred plan will be made in June and construction of the new connection will begin in 2029, he said.

Auckland is home to nearly a third of New Zealand’s five million people and faces extensive peak-hour congestion as residential and commercial activity has burgeoned. The harbor effectively splits the city in two and the growth has put increased strain on motorways and the existing bridge that was opened in 1959.

“Aucklanders and businesses have made it clear that the biggest barriers to the success of Auckland is persistent congestion,” said Wood. “It’s vital that we have a harbor crossing that works for the city.”

Options include a new road and rail bridge next to the existing bridge, or two separate road and rail tunnels. Variations include bridge and tunnel combinations.

Each scenario includes a new walking and cycling link and a new light rail link that will connect to the proposed Auckland light rail system, Wood said.

No cost estimates or funding plans were released. Wood told reporters that details will be finalized in the next stage of the process when the business case is developed based on the option chosen. Tunnels are more expensive, he said.

“It will be a significant investment, in the billions of dollars, and that will be shaped by the options we choose,” he said. “We will work on the costings as we move into the detailed business case.”

Construction on this scale will take many years and needs to be integrated into other Auckland projects, Wood said. By providing a clear option early, the construction industry will have a better pipeline of work allowing it to prepare resources and labor, he said.

The government previously said it would consider a second harbor crossing beyond 2030. Prime Minister Chris Hipkins will now have a plan in place ahead of the October general election, and he expects opposition parties to back it.

“I don’t think there’s going to be any shortage of cross-party political support for a second Waitemata Harbour crossing,” Hipkins said. “These projects take a long time and you need to see them through from start to finish. We are locking in a commitment to make this happen.”

(Updates with minister’s comments on cost in seventh paragraph)

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