One of the many reasons why I oppose an additional road crossing of the Waitemata Harbour (along with the insane price tag and the horrific environmental effects) is that I simply don’t think it’s necessary. Let’s take a look at monthly averaged daily traffic flows across the Harbour Bridge over the past few years – thanks to this excellent data from NZTA: The gaps in the data (it would be really nice having the earlier months in 2007 in particular) limit comparison to some extent, particularly as 2008 was an incredibly unusual year for traffic volumes (it’s when petrol prices skyrocketed through $2 a litre for the first time). However, overall it seems the general trend has been downwards over the past few years.

Looking at annualised average daily traffic counts, you get the same story – once again thanks to NZTA’s great data: There are a number of potential reasons for such a change: less general travel between the isthmus and the North Shore might be the result of greater employment on the Shore, higher petrol prices discouraging travel, a static economy also discouraging travel and so forth. The other reason could be a shift in people from cars onto public transport – thanks to the Northern Busway, which just happened to open in early 2008.

Looking at peak time flows of people over the harbour bridge, it would seem that the number of people crossing at peak times has continued to increase over the past few years – mainly through a big upswing in bus usage: From looking at the graphs above it seems pretty clear that the Northern Busway has got people out of their cars and onto the bus. While general travel between the North Shore and the isthmus has continued to increase, this hasn’t led to more cars crossing the bridge – instead we have actually seen a fairly significant decline since 2006/2007, just before the Northern Busway opened.

These statistics tell me that it’s not a simple inevitability to expect traffic volumes to increase in the future – in fact they’ve been doing quite the opposite in recent years. While the number of people crossing the bridge seems likely to increase, as our population grows, there’s no reason why that has to require more general traffic lanes, if what’s happened over the past few years is anything to go by. Plus of course, if we need to cater for many more people between Akoranga and the city centre, we could always build a railway line for half the price of the road option.


Looking at traffic flows along all parts of the Northern Motorway over the past five years, it is interesting to note that the area with the least increase (Esmonde Road to Fanshawe Street) is exactly the same area of the motorway proposed for effective duplication with the additional crossing:

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  1. My reading on the last table is that the number of vehicles using Fanshawe St off ramp has dropped from 44000 to 35000. That is about 20%, and is where competition from buses would be most intense.

  2. And then if there is congestion on the bridge there is the question of whether to do anything to lessen the congestion. See

    If you ease the congestion by building more road space it just puts more people in cars and it is soon congested again. That equals pissing a lot of money up the wall for no net gain, and an environmental net loss. A lot of motorway projects in reality probably have negative BCRs and they’re throwing good money after bad, when really it is better to not chase sunk costs.

    It’s probably time to reserve more of the bridge’s roadspace for buses, improve ferry services, and in the long term consider north shore rail.

    1. exactly Matt, and the terrible cost to the already degraded quality of life on Auckland’s streets, and the absurd waste of money and land providing storage for those vehicles. And not just once, mandated offstreet parking at your home, then the same again at the mall and the office…. crazy. Building office space for a staff member and their car needs twice floor area, of just the human without the machine, this all has to be paid for, as well of course for the endless building and rebuilding of the motorway network we see all around us. Yet there are twonks who claim that this car only system is the most economic and best way to order our city. #crazymath.

      1. Most offices still require car parks for sales reps etc who have to spend time in the office and on the road however, as has been proven, if the public transport is regular, well priced and in the right places, it will succeed in getting cars off the road. I believe one lane on the harbour bridge (alternating from morn – afternoon) should be bus only.

        1. Customers, visitors etc. I’m agreeing with the idea but the reality is there still needs to be parking during the day. Is the argument about congestion during rush hour(s) or getting cars off the road? There is a very important difference between the two.

  3. Bryce yes you are thinking like an Aucklander, business, indeed life is unthinkable without at least one car per person immediately on hand! There are plenty of old and new buildings in AK without a single car space in them, they are leased and the businesses function. In fact those leaseholders are not paying for a whole lot of vehicle parking and circulating space in their rent. It is crazy that the council makes building owners waste money and land on this.

    But also because we have only been investing car travel we have made it natural to think like you are. This is the whole point of the changes we are trying to make, the more the quality of alternatives to driving improve the more people will discover the advantages and cost savings that can be made by not always using a car…. and of course they will be freeing up the existing driving infrastructure for those who still choose or feel they need to drive….

    Your argument only has weight if we were proposing to ban all driving, and of course that isn’t true, just urging investment in a city with more choice for everyone. More freedom in fact. ‘Cos there ain’t no freedom of the highway when everyone has to do it all the time.

  4. I, for one, could not carry out my daily business without my car. Getting to work at 6am, in a different place pretty much wvery day while carrying 100kg’s of gear would not be too practical. Likewise a builder or plumber. Luckily I very rarely have to travel at peak times, usually before and after they have occurred. My wife works from home but also has to visit various offices. To do this using public transport would be very time consuming. Your concept is based around the cbd and the general office worker who stays in the one place all day. I read this blog as someone who believes better public transport will supplement automotive use around the city, not replace it.

    1. But Bryce can you imagine that there are others who have different routines, and that yours and your wife’s could be a lot easier without everybody on the roads all the time too? There is no attack on your ability to drive here, no roads being ripped up, just the existing network being complemented by a new one that will go a long way towards keeping the roads freer for longer.

  5. If you read my posts you will realise that our views are very similar. Indeed, I support closing a lane of the bridge (changing as the traffic flows change) and do not think we need another car crossing but a rail tunnel crossing is imperative.

  6. this analysis really needs to be undertaken with directional figures, not just AADTs, what I have observed over the 17 years that I have lived on the Shore is a growth of “contra-peak” trips and a decline in “peak” direction trips

    this effect is particularly evident on a Friday afternoon when the moveable lane barrier appears to CAUSE southbound congestion while northbound traffic runs very freely

    further, if you look at the bar graph it becomes evident that on a person trip basis, dedicating lanes to buses on the bridge is not only justifiable, but the decreased travel time would further improve the bus service attractiveness and efficiency

    I think that the primary real argument for duplicating or replacing the AHB is the fatigue life of the structure(s)

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