Double decker buses are now a common sight on the Harbour Bridge since Auckland Transport started using them for the Northern Express in 2013. If mayoral candidate John Tamihere gets his way it won’t just be the buses that would be double decked but the bridge too. On Friday he released a plan to replace the existing bridge slide a new double decked structure on to the existing piers.

“A new 10 vehicle lane Harbour crossing, which will carry cars, rail, pedestrians and cyclists can be completed within 6 years on the existing bridge piers, replacing the existing bridge,” Tamihere said. “There will be minimal disruption to traffic

He gives more detail about the idea in a separate document, including this

The superstructure replacement process is: Build new AHB superstructure on temporary piers to the east ofthe existing bridge;

Switch road traffic to the new superstructure;

Remove the old superstructures from the existing piers;

Slide the new superstructure west, over 24 hours, to its final positionon the existing piers;

Allow traffic to flow on the 2 footpaths, 2 cycleways, 10 road lanesand 4 rail tracks on the new superstructure in its permanent position. Full or partial superstructure replacement has been carried out on a number of bridges in the United States including the Milton-Madison Bridge over the Ohio River which was built in 1929. Its superstructure was replaced in 2014 at a cost of USD $103.7m.

Below are some thoughts about the idea.

Is it practical?

As Tamihere has said, this was done on the Milton-Madison Bridge over the Ohio River. However a quick look at Wikipedia suggests this is a significantly difference scale. The Milton-Madison bridge is a two-lane bridge that was replaced with wider two lane bridge (and footpath) and it only carries about 10,000 vehicles as day. By comparison our Harbour Bridge carries about 171,000 vehicles per day but even more people due to around 50,000 people crossing on buses.

It also says they had to close the bridge to all traffic for 15 days while they slid the new superstructure in to place. That’s a lot more than the 24 hours Tamihere claims and would be some serious disruption even if it took place over the quieter Christmas/New Year period.

It’s not a local project

It’s all very well to propose the Harbour Bridge be replaced but this isn’t something the mayor has control over as the bridge is owned and operated by the NZTA. Tamihere claims this isn’t a problem, saying: “Who cares? They do as they’re told. They’re bureaucrats“, however, even if that were true, they’re accountable to the government.

Of course, as Mayor he could advocate for the government to support the idea but who knows how long that could take.

It doesn’t really add any road capacity

The plan is for 10 road lanes, and while that’s more than the eight we have now, the movable barrier means that we already operate the bridge with 5 lanes in the peak direction anyway. This means ultimately, you end up with the same issue the NZTA have with their road crossing proposals. You either add more capacity and make congestion worse as well as undermine goals to improve the city centre or you spend a heap of money to add no real new road capacity, in which case, what’s the point.

It’s also worth remembering that earlier this year the NZTA confirmed the best option for a new crossing was one that was light rail only.

It seems the only real benefit from this proposal is the addition of the PT and active modes but then why not just deal with those on a new dedicated crossing instead of trying to shoehorn them onto the existing bridge with all the compromises that would entail.

How does it connect

Perhaps the biggest issue with the proposal is the question of how it all connects.

A 10-lane bridge is wider than what we have now, and so the bridge would have even greater impacts have on Northcote Point and St Mary’s Bay? As we’ve seen in the past with Skypath and past widening of the motorway through St Mary’s Bay, those residents aren’t afraid to make their voices heard.

Adding a second deck to the bridge is one thing but at either end those people and trains up the top somehow need to be able to get on and off the bridge. Once it’s off the bridge, where does the rail line run, and how does it connect to the city and the rest of North Shore? The cost to do those connections, let alone the amount of space that might be needed could be substantially more than a new purpose-built bridge (or tunnel) on a better alignment.For those mode obsessed people out there claiming all new rail lines should be heavy rail connected directly to our existing lines, it’s also worth noting that the existing bridge is too steep and so this would have to be some form of light rail.

The connection issue also applies to pedestrians and cyclists who would also have to somehow get up above those traffic lanes. This is likely to make it even harder for those with limited mobility.

It’s not all bad

For all its issues, it is probably less crazy than the NZTAs plans for another crossing which their own analysis shows will only make congestion worse. One thing I particularly like about the proposal is the inclusion of four tracks allowing for rail connections to both the busway and perhaps up the western North Shore. This is something we’ve suggested in the past too as it gives a greater opportunity to address future capacity needs and is something that’s much easier to future-proof for with a bridge than a tunnel. There’s also a huge amount of space for cyclists and pedestrians.

I also think it’s good that we have a discussion about the merits of a cheaper bridge for any future (PT + active only) crossing as opposed to a tunnel.

Be more creative

Even if this idea was feasible and affordable, if we were to go to the all the trouble to replace the bridge structure, why would we replace it with something that looks the same as is and not with something less ugly.

Goff’s Response

For his part Mayor Phil Goff is rubbishing the idea saying:

The 18 lane harbour bridge that John Tamihere is proposing would cost over $10 billion to build. — Phil Goff (@phil_goff) August 16, 2019

It feels like Goff just pulled the number out of thin air given I can’t recall seeing a suggestion like this before in any of the many NZTA studies over the years. The idea is silly enough on it’s own that it doesn’t need made up numbers to make it look worse.

Penlink

The final part of Tamihere’s announcement was that he would commit to building Penlink. Noting:

The 7km Penlink road, consented to run between the Northern motorway and the heart of the Whangaparaoa Peninsula, will reduce traffic flow by an estimated 50,000 vehicles per day through the Silverdale Business area. Almost 130,000 vehicles a day travel through the heavily congested business area.

A few quick comments on this

Penlink is already committed to and is listed as a decade 1 project as part of ATAP. The biggest thing that prevents it from happening sooner is the cost, now estimated at around $400 million.

The text above is almost word for word from a Chamber of Commerce press release. It was wrong then and is wrong now. For example: The business case expects just 16,800 vehicles a day to use Penlink in 2046. That’s not close to the 50k claimed. Auckland transport’s Traffic count numbers, suggest that fewer than 50k vehicles use the Hibiscus Coast Highway road through the business area daily, even at the motorway end. This is backed up by … The NZTAs motorway data shows 38k vehicles use the ramps at Silverdale with most (about 32k) using the south facing ones.



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