The preferred option for a new harbour crossing in Auckland is four tunnels that do not compromise council plans to redevelop the city's harbour front.
Two of the tunnels will be part of State Highway 1 with three lanes northbound and three lanes southbound in total. The other two are for electric trains.
The price tag is a whopping $3.7 billion and $4.1b for a "preferred option".
Another option with longer motorway tunnels through to central city Grafton Gully has a price tag of $4.7b to $5.1b.
Today's media release by Auckland City Council, Auckland Regional Council, Auckland Regional Transport Authority, North Shore City Council and Transit New Zealand did not say who would pay.
Up until now the front runner idea for a new harbour crossing had been a new bridge. The problem was that the best place for it on the city side was the Wynyard Quarter, an area councils want to develop into an upscale new harbour front suburb.
Auckland Regional Council has acquired the land for this ambitious harbour front development from Ports of Auckland, which it now wholly owns. The land currently has fuel tanks on it.
A lot of investment has also gone into a western road route but Auckland leaders also want a new harbour crossing, arguing there will be an 80 per cent increase in trips across the harbour by 2041.
The Waitemata Crossing Study released today said a bridge would be the easiest to build and less expensive option but it would also be disruptive to the waterfront.
There had been a change of thinking on the previous recommended Esmonde Road (Takapuna) to Wynyard Point route.
The Waitemata Crossing Study team whittled 159 options down to three and have now come up with a preferred option.
The motorway tunnels in the preferred option would go under Victoria Park, just north of the city centre, before surfacing to link to the Southern and Northwestern motorways within the Central Motorway Junction.
Tunnel portals south of Cook Street would be within the existing motorway corridor. The Victoria Park flyover would be demolished.
The rail tunnels, one track northbound, one southbound, travel eastward under Gaunt Street to link with a future CBD loop rail tunnel.
There will be an underground station in Gaunt Street, between Daldy and Halsey Streets, to serve the Wynyard Quarter.
The Auckland Harbour Bridge could be used to extend the northern busway into the city centre, or the bridge "clip on" lanes could be removed altogether.
The Auckland Harbour Bridge carries more than 160,000 vehicles per day, or nearly 60 million vehicles a year.