A detailed study will be conducted into the route of a possible underground rail tunnel through downtown Auckland.
State-owned company KiwiRail and Auckland's regional transport agency (ARTA) will look into the underground route that would link the Britomart rail terminal with the Mount Eden railway station.
The cost of a twin-track tunnel is estimated to be more than $1 billion and the study should be finished by the end of next year.
ARTA chief executive Fergus Gammie says the rail tunnel would have the biggest transport impact on Auckland's central city since the opening of the Harbour Bridge 50 years ago.
