Trackless trams will not be recommended to the Government as an alternative to the proposed light rail line from the city centre to Māngere.
Nor will an extension of the existing rail network.
And in a further twist, the option that seems to be favoured will not include trams running up Queen St. Instead, they would run from the Wynyard Quarter west to east across the city centre, through a tunnel that crosses under Queen St.
The Auckland Light Rail Group (ALRG), set up by Government and Auckland Council, has largely completed its business case analysis of the options and will report to its board next week.
The board's recommendation will go to the Ministry of Transport, which will prepare a briefing paper for Cabinet in November. A Government announcement is expected before Christmas.
The ALRG considered a long list of possibilities, including trackless trams, three heavy rail options, a monorail and Elon Musk's hyperloop, and produced a shortlist of three. One is "light rail", which means modern trams running on tracks on the roads, with frequent stops.
The second is "light metro", which means trains running underground through built-up areas, with larger trains and fewer stops. The third option is a hybrid of the two.
The project is known as CC2M: the City Centre to Māngere line. It will start in the Wynyard Quarter and end at the airport.
ALRG's lead on the business case, Cameron Law, confirmed to the Herald yesterday that if it's light rail, it will run up Queen St and then down the Dominion Rd corridor – either on that road or on Sandringham Rd – to Mt Roskill, Onehunga, Māngere township, the airport industrial zone and the airport itself.
The definite inclusion of Onehunga and Māngere township on the route is new.
Light metro would also start in Wynyard, but would be tunnelled under Midtown with a connecting stop near the CRL's Aotea station and another stop at the universities.
This is also new: the crosstown route has featured in confidential proposals before but has never been made public.
The metro option would also be undergrounded from the top of Dominion Rd all the way to Mt Roskill, but after that would follow the same above-ground route to the airport as light rail.
The choice between light rail and light metro is far from easy.
Both options, said Law, would take about 10 years to plan, consent and build. That's hard to grasp: laying tracks on the road will take as long as digging the longest tunnels the city has ever seen?
Light rail would be more disruptive to build. The idea of years more roadworks on Queen St and Dominion Rd will fill many people with horror. The possibility of keeping public transport out of Queen St, offered by light metro, may appeal widely too. We could bring back the Waihorotiu stream.
The tunnels for the metro option would be bored. The "cut and cover" digging process used on Albert St for the CRL will not be repeated.
Light metro is also faster: end to end, the ALRG says it would take about 27 minutes. That's good for most commuters and for people wanting to catch a plane. But the difference isn't immense: light rail would take only 10 minutes longer.
Light rail, with many more stops, offers a better service for people along the way. If you're getting to school, going shopping, visiting friends, off to the doctor, light rail will probably be easier. It's a gendered issue, too: those things relate more to women than men.
But light metro easily wins on capacity. The table shows the per-hour passenger capacity: the numbers translate into each light metro train carrying 580 people; light rail about 420.
That means, said Law, the metro option would be at full capacity in about 80 years; light rail in half that time.
What about the cost? They're not saying, yet. But it's clear that with all the tunnelling, light metro will cost billions more to build than light rail.
Despite that, Law said, because of the capacity difference, the business case analysis for both options is much the same.
"The costs and benefits go up at about the same rate," he said. "You get what you pay for." He seemed to be suggesting light metro is preferred.
But why do it at all? Just using more buses would be much cheaper. So would trackless trams. And there are those three heavy rail options, too.
The core purpose is to build a bigger transit network, offering a reliable and appealing service "in a corridor that is home to nearly 200,000 people and growing fast". Buses can't do it, partly because their capacity is limited and also because there's no room for them. The city centre clogs up with buses now.
Trackless trams have two big problems. They're really heavy, which means the entire route has to be dug up and strengthened. So that's disruptive.
And they carry only about 170 people per tram. The ALRG says trackless trams heading to town from Māngere during the morning peak would be full by the time they got to Mt Roskill.
In cities using them overseas, there have been problems with reliability, ride quality, navigation system faults and other issues. That's led to trackless tram systems being "retired" in France, Britain, the Netherlands and the US.
So why not just extend a rail spur to the airport from Puhinui station, which is on the existing Eastern and Southern Lines? Because, says ALRG, it does nothing for the fast-growing populations of Māngere, Onehunga, Mt Roskill and the Dominion Rd corridor.
Why not extend the Onehunga line, then? Auckland Transport says this is viable, although expensive, and it would serve Māngere well.
But trains from Onehunga to the city centre would still not be running near Mt Roskill or the Dominion Rd corridor. To cater for the 60 per cent of passengers who missed out because of this, they would still need a rapid busway or even a light rail line.
Might as well build it properly.
Or extend the idea? The third option is a new track from the Western Line at Avondale down to Onehunga and then Māngere township and the airport.
That would cater to Mt Roskill, but it doesn't help with demand on the Dominion Rd corridor, so more buses would still be needed.
The strategic goal of Auckland's mass transit planning is to create a broader network, serving more catchments. The CC2M line is one of many that, over the next decades, will be built to serve the city's north, west, east and south.
The heavy-rail options for CC2M don't broaden the network. They fill up the existing lines more quickly than would otherwise have happened, offer little to those people who don't already live near a line and therefore increase the demand for buses.
For the Government, the politics of the issue may be more important than the true merits of each option. What's worse: the disruption of light rail or the cost of light metro?
Meanwhile, there's a pretty good transit option to the airport already. You catch the train to the new Puhinui interchange station, then the new shuttle bus that takes 10 minutes on a dedicated lane. In peak times, helicopters aside, it's the fastest way to do the trip.