KiwiRail would like to cut the Aratere ferry in half and fit a new 30m section to it, fit rails to the Kaitaki ferry and replace the Arahura ferry by 2015.
It would also like a new ferry terminal in Wellington and a new port at Clifford Bay south of Blenheim to improve the travelling experience of tourists and cut 20 minutes sailing and 50 minutes driving time from an trip between Wellington and Christchurch.
In a capital-constrained world it is not all going to happen but the "jumboisation" of the Aratere is the top priority and may be achieved before next year's rugby world cup.
The revival of the Clifford Bay concept has not made it anywhere near an official strategic plan but it is still being tossed around as an idea that could be "turned on" in the offices of the Interislander, the business which operates KiwiRail's ferries.
The Interislander operates three ferries, only one – the 25-year-old Arahura – of which is still owned.
The ferries are losing foot passengers to airlines offering cheap fares and passengers are increasingly travelling in larger cars with bikes on the back and camper vans, which take more space.
The ferries are a key part of the rail network and two of the three ferries, the Arahura and Aratere, have rail decks.
It is this part of the business that is running into constraints as companies such as Mainfreight and Toll New Zealand put more national freight on rail.
Thomas Davis, general manager Interislander, is clear about one thing – without rail-capable ferries there is no national rail network. It takes too long to unload containers from a freight train on one side of Cook Strait, load them on a ferry and then load them back on a train on the other side of Cook Strait.
"The ferries have to be rail capable," he told NZPA.
Currently the Kaitaki is not rail equipped, and the Interislander is looking at fitting them. This is not that difficult from an engineering perspective though tanks have to be fitted to balance the ferry.
The problem is that the Kaitaki is 20m wider than the two other ferries and does not fit in the existing ferry terminals; it would be expensive to rebuild them.
The vessel is also only leased for another three years. To justify the expense it would have to be purchased or leased for a long time.
The Arahura is "long in the tooth" but had a $9 million refit in 2008. It was designed before deregulation of transport.
"In terms of ability to suit the current market the Arahura is at the limits of capability," Mr Davis said. The vessel is now capable of carrying 539 passengers, down from around a 1000 when it was delivered in the early 1980s.
The Kaitaki can carry 1650 passengers.
KiwiRail will next year start examining options for replacing the Arahura by 2015 or 2016. These include buying a new ferry or leasing an existing ferry and making it rail capable.
There are only about a dozen or so rail-capable ferries in the world and New Zealand has two of them, according to the company.
The company's immediate priority is a project to lengthen the Aratere. By increasing the length by 30m the company creates 120m of rail capacity, as there are four rail lines on the rail deck.
The new section would be built prefabricated and fitted. An issue with the project is that the Aratere is leased so the vessel would have to be refinanced before it could be rebuilt.
The new section could be built this year and fitted in March next year so the vessel could return in July ahead of the Rugby World Cup.
Mr Davis said the Interislander business was profitable and cash positive but he would not disclose financial information for it.
His argument is that this part of KiwiRail has a strong business case for capital investment, whether it is from the government or from utilising the cashflow it produces.
"We have a sound business case for the Aratere extension," he said.
The company also wants to reshape the bow of the Aratere to reduce fuel consumption and reduce the size of the waves the vessel creates.
The "jumboisation" of the Aratere will increase its passenger capacity from 350 to 600 and add 25-30% to freight capacity.
The Interislander business has also been in talks with Wellington's CentrePort about ferry terminal facilities. The terminal does not have enough marshalling space and Mr Davis admits it is like Wellington's airport before it was redeveloped.
The company is interested in reclaimed land the port has near the existing terminal.
A briefing to incoming ministers in 2008 said the Interislander owned the Wellington arrivals terminal building and the majority of land holdings at the terminal while CentrePort owns and maintains the departures terminal, gangways and link-spans.
Port of Marlborough owns and maintains the Picton terminal building, gangways and link-spans. The land ownership is shared between Interislander and Port of Marlborough.
The briefing said the development of a new port at Clifford Bay was in abeyance but not off the agenda.
The briefing also said both CentrePort and Port of Marlborough regard the Interislander as a captive customer and are not prepared to reduce port costs of $10 million a year.