Explainer | Why isn’t there a tunnel connecting New Zealand’s main islands?

A Cook Strait tunnel would dramatically reduce travel times. But unlike in Britain and Japan, New Zealand has not seriously considered it

Reading Time:3 minutes

A ferry crosses the Cook Strait in rough seas on its way to Wellington, New Zealand. Photo: Stuff via AP

Published: 3:26pm, 8 Jan 2025

Wild weather during New Zealand’s peak summer holiday period has disrupted travel for thousands of passengers on ferries that cross the sea between the country’s main islands.

The havoc wrought by huge swells and gales in the deep and turbulent Cook Strait between the North and South Islands is a recurring feature of the country’s roughest weather. Breakdowns of New Zealand’s ageing ferries have also caused delays.

But unlike in Britain and Japan, New Zealand has not seriously considered an undersea tunnel beneath the strait that more than 1 million people cross by sea each year. Although every New Zealander has an opinion on the idea, the last time a prime minister was known to have suggested building one was in 1904.

A tunnel or bridge crossing the approximately 25km to 30km (15 miles to 18 miles) of volatile sea is so unlikely for the same reason that regularly vexes the country’s planners – solutions for traversing New Zealand’s remote, rugged and hazard-prone terrain are logistically fraught, analysts said.

An train emerges from the undersea tunnel that connects Britain and Europe by rail. Photo: AFP/Getty Images/TNS

Why isn’t a tunnel practical?

A Cook Strait tunnel would dramatically reduce the three- to four-hour sailing time between the North Island, home to 75 per cent of the population, and the South Island.