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.
They predict cuts in travel times to central Auckland throughout the rail system, but notably on the western line, on which 25 minutes are expected to be slashed from what are now 39-minute trips from Morningside, and 28 minutes from 51-minute rides from New Lynn.
Better and faster public transport is expected to encourage a more than trebling of central Auckland's population, to about 78,000 people by 2040. It is also predicted to contribute 5000 of at least 55,000 new jobs expected to be added to the city centre's workforce.
The draft Auckland Plan says transformational effects of the project will extend to development opportunities and intensification along its contributing railways lines, which should also be supported by extra park-and-ride facilities.By Mathew Dearnaley Email Mathew