Since our post on Wednesday about NZTA’s briefing to Minister of Transport Phil Twyford on the Additional Waitemata Harbour Crossing project, most media outlets have covered the report and started exploring the issue. Quite a lot of them have picked up on issues like a new harbour crossing funnelling more traffic into the city centre, or on the pros and cons of different forms of rail for the future rapid transit crossing. But there has been relatively little coverage of what I think is the most startling and compelling finding from the briefing – that the road crossing makes traffic worse. Remember the key graph from the briefing:

The key bars to compare are the left-most green bar with the third and fourth green bars from the left. These show that spending many billions of dollars on a massive new road crossing in addition to a light rail crossing actually slow down (or at the very best doesn’t speed up) traffic speeds across Auckland.

This finding isn’t particularly surprising, as it is entirely consistent with transport modelling undertaken in 2016 as part of the Auckland Transport Alignment Project. This modelling looked at 2046 congestion levels with and without the crossing – and basically found that the new tunnel would be just as congested (if not more so) than the Harbour Bridge would be without the project:

It’s also worth remembering the huge damage this project would bring. For example the 2010 proposals would see huge cut and cover tunnels underneath Victoria Park – which would likely require the removal of many of the large trees that go around the perimeter of the park, as well as the potential demolition of buildings such as the Air NZ building on Fanshawe St and the historic Victoria Park markets:

There’s no information in the briefings on the project’s likely cost. However work done nine years ago estimated a cost of around $4.8-5.3 billion and for a few reasons it’s likely this might have doubled by now:

NZTA is now looking at a much longer tunnel – maybe around 6 km compared to the earlier proposal of around 3.6 km.

NZTA accept that the Northern Motorway would need to be widened all the way up to Constellation Dr/State Highway 18, as part of the project.

Construction costs have increased a lot over the past decade. The City Rail Link’s estimated cost back in 2012 was around $2 billion, and it’s now rumoured to actually cost about double that amount.

So we have a destructive project that might cost north of $10 billion, that actually makes traffic worse and floods the city centre with cars, completely contradicting all strategic guidance. Yep it’s pretty bad.

It does beg the question of why this is such a bad project – at least from a “why doesn’t a heap more traffic capacity across the harbour help reduce congestion?” perspective. The answer of course is partly to do with the well-discussed phenomenon of induced traffic demand, where additional road capacity encourages people to drive more and clogs up the roads again quickly. But also partly it is because providing extra capacity over the harbour is pretty useless when you don’t have spare motorways and local roads on either side to connect into this new crossing. Ultimately the tunnels just link back into the same motorways and local roads to the north and south, meaning that they don’t actually create a better overall transport network.

Just look in the map below – ultimately the additional crossing (red) is just duplicating a very small part of State Highway 1 (blue). Whatever your thoughts on the Western Ring Route (green) and in particular the Waterview tunnels, at least those projects have delivered a new route that provides additional network connections and resilience.

In some respect I can understand why people like former North Shore City Mayor George Wood push for this project so strongly. Congestion on the Northern Motorway at peak times can be pretty nasty and I think if you’re staring out of your windscreen, there’s a general assumption that building another crossing would fix this problem for good. Unfortunately that seems to simply not be the case and a massively destructive and almost incomprehensibly expensive new motorway tunnel would, if anything, actually make traffic worse.

Share this