New road shapes as a costly blunder

After being on the back burner for decades, Transmission Gully is now on the fast track.

It's been given the green light by a fast track consenting process, and work on the motorway is to begin in 2015.

The Government is intending to fund the $1.3 billion motorway through a public private partnership. Under this arrangement, a private consortium will finance, build and operate the motorway for 25 years, and the Government will pay the consortium $130 million a year, or $356,164 every day, for the next 25 years.

There are widely varying estimates of how many commuters will use Transmission Gully. But using the New Zealand Transport Agency's projection of about 20,000 a day, the taxpayer will end up subsidising every commuter who travels on the motorway to the tune of about $18 a day.

That's an awful lot of money to spend on a motorway that is so steep in parts that trucks are unlikely to use it, and which could take even longer to reopen in an earthquake than the coastal route.

The main justification for building Transmission Gully has always been that it will provide an escape route out of Wellington in the event of a serious earthquake.

It has, therefore, always struck me as odd that a road intended as an escape route out of Wellington would be built on or close to an active fault line.

A confidential 2008 Ministry of Transport briefing paper on Transmission Gully, obtained under the Official Information Act, points out that the heaviest engineering works on the motorway, including a viaduct, are to be built on the route's most earthquake-prone section.

The NZTA estimates that, despite this, the motorway could reopen "within as little as three weeks" after an earthquake. But the briefing paper notes that another opinion estimates it could take substantially longer than the coastal route to reopen after an earthquake.

This is understandable, when you consider that bulldozers could remove a major slip on the coastal route directly into the sea, whereas a slip on the incredibly steep sections of Transmission Gully could make the area as difficult to reopen as the Manawatu Gorge.

The board of inquiry that approved Transmission Gully admitted the route was "at risk of closure in an earthquake", and that parts of it could be closed for between three weeks and three months.

That hardly sounds like an escape route.

The other issue that has been largely overlooked is how many people will choose to drive on such a steep motorway.

For a 3-kilometre stretch, it will be way steeper than the Ngauranga Gorge, and twice as long. It will be so steep in fact that, according to the briefing paper, an "escape ramp" and an "arrestor bed" will have to be built for "out of control vehicles".

This begs the question: How many Kapiti residents will be prepared to commute daily down a stretch of motorway that is far steeper and twice as long as the Ngauranga Gorge, especially when there is a pleasant, low-lying alternative coastal route, and when they will probably have to pay a toll for the privilege of driving on this treacherous stretch of road? I mean how many people would willingly commute over the Rimutuka hills if there was a safer, flatter, alternative route?

Certainly large trucks won't want to use the route, according to the briefing paper, as it will be way too steep for them.

This is ironic, as much of the pressure to build Transmission Gully (and all of National's roads of national significance) has come from the trucking lobby, which donated generously to the National Party before the last two elections.

Clearly the trucking industry is hoping that most commuters will use Transmission Gully, and this will free up the coastal route for trucks. That will not please residents in Pukerua Bay who are hoping that juggernaut trucks rumbling through their community will end when Transmission Gully is built.

The board of inquiry admitted there's a wide disparity in the projections about how much traffic will use the motorway, especially if there is a toll.

The Government has now confirmed it is investigating a toll, which could reduce traffic volumes steeply. So too could rising oil prices, if commuters decided to switch to trains to commute to Wellington.

What if a combination of rising oil prices, a highway toll, and commuter reluctance to drive on the steep and treacherous route were to halve official forecasts?

The Government would still be locked into paying more than a $1 million every three days, regardless of how few cars used the motorway.

If this happened, the economic benefit of the project would plunge below its already minuscule cost benefit, and Transmission Gully would become an expensive white elephant, and a constant, huge drain on the taxpayer purse.