Why a Sydney-Newcastle high-speed train link would need some of the world’s longest rail tunnels

More than half of a 140-kilometre high-speed train line between Sydney and Newcastle would need to comprise tunnels because of hills, national park and built-up urban areas, resulting in the link having some of the world’s longest rail tunnels if it becomes a reality.

Under the early scope for a dedicated high-speed link, up to 84 kilometres primarily between Gosford and central Sydney is set to comprise twin tunnels if the federal government makes an investment decision to proceed with the ambitious project as early as next year.

An artist’s impression of a high-speed train in a tunnel on a Sydney-Newcastle line.

Underscoring the challenges, the longest of the continuous underground sections along the proposed route is set to be about 38 kilometres. In comparison, the Gotthard Base Tunnel under the Swiss Alps is the world’s longest rail tunnel at 57 kilometres.

The indicative size and scale of the Sydney-Newcastle connection have been outlined by the High Speed Rail Authority, which will hand a business case for the megaproject to the Albanese government by the end of this year.

High Speed Rail Authority chief executive Tim Parker said tunnels from Sydney to Gosford were considered the most practical option because of the constraints imposed by national park, the area’s topography and the Hawkesbury River.

“It’s without doubt the most difficult terrain,” he said. “It would certainly be longer than most tunnels, but that’s the reason why you try and break it up into a series of sections.”

High Speed Rail Authority chief executive Tim Parker.Credit: Louie Douvis

The “emerging scope” for the project entails the first stage of the high-speed line terminating at Central Station, instead of Olympic Park as under previous state government plans.

Parker said the rationale for extending it to Central Station was “all about connectivity”, adding that it was vital to locate the stop in an area where most people could access it.

“That’s why Central will be the right location,” he said. “It means whoever wants to use it can get there either by Metro or Sydney Trains,” he said.

While Hornsby has been under consideration, Parker indicated Central Station and Gosford were likely to be the only stops between Sydney and the Central Coast.

If it proceeds, about 25 kilometres of the entire line would comprise viaducts or bridges – most of which would be on the section between Gosford and Newcastle.

A map shows the distance a high-speed train will travel in an hour between Newcastle and Sydney compared to a car or intercity train.Credit: High Speed Rail Authority

The authority is also considering an alignment for further stages of high-speed rail from Central Station to stops at Parramatta, Western Sydney Airport and on to Canberra.

Parker said completion of the business case by the end of the year would allow the federal government to make an investment decision in 2025 and, if given the green light, could result in the first contracts being awarded by 2027.

Parker, a former senior executive at Sydney Metro, will outline his vision at the Australasian Railway Association’s inaugural high-speed rail conference in Sydney on Wednesday.

Australasian Railway Association chief executive Caroline Wilkie said a massive project like high-speed rail offered significant economic benefits, and the construction phase alone would create thousands of jobs from engineering to manufacturing and supply chain logistics.

“This would offer a much-needed boost to the economy, particularly in regional areas that would benefit directly from construction projects and the influx of workers,” she said.

Under the early scope, high-speed trains would travel at speeds of at least 250 kilometres an hour, making the journey an hour from Newcastle to Sydney. A trip from the Central Coast to Sydney or Newcastle would be about 30 minutes.

About 20 trains comprising eight carriages would be needed for the high-speed line, which would be separate from the existing passenger and freight train line between Sydney and Newcastle.

Parker said the cost of a high-speed link between Sydney and Newcastle “will be expensive”, and would form part of the business case.

A British rail expert, Professor Andrew McNaughton, who led a review for the Berejiklian government, has said that the cost of a fast-rail link from Sydney to Newcastle would easily run into the tens of billions of dollars because of the need for tunnels under Sydney and the Hawkesbury River.

However, McNaughton has said it would offer high benefit, and the reason a Sydney-Newcastle link should be prioritised is that it has “banks of potential”.

The Albanese government has committed $500 million to plan for and protect a corridor for a high-speed rail line between Sydney and Newcastle. About $79 million is going towards the business case.

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