Opening up Britomart with a 3.5km rail tunnel is "the foremost transformational" project in the first decade of the 30-year plan, says the Auckland Council's plan.
The document says the proposed $2.4 billion two-way link, which would include three new underground stations, received overwhelming support in public responses to the Auckland Unleashed discussion paper.
It would create the city's "most significant place-shaping" opportunity by allowing increases in train frequencies across the entire rail network, which is otherwise expected to be constrained from next year by the limited capacity of the dead-end Britomart station.
Despite Government scepticism about how many vehicles will be removed from city streets, as opposed to passengers merely swapping from buses to rail, the planners believe faster trips to more parts of downtown Auckland will persuade people to leave their cars at home.
They say the tunnel will allow the reorganisation of bus routes, with an emphasis on rail feeder services, taking pressure off city roads which are already becoming clogged.
