Traffic volumes on Auckland’s motorway system

The agenda for Tuesday’s meeting of the Auckland Council Transport Committee has been uploaded (part 1, part 2) and there are a number of interesting items. Perhaps the most interesting will be a presentation and discussion on the CBD Rail Tunnel project – which it seems the council is now officially calling the “City Rail Link” (isn’t that what I suggested a few months back?) It will certainly be interesting to see what comes out of that presentation, and also what direction the Council gives to their staff and to Auckland Transport about advancing that project further – beyond of course the designation process. I will discuss possible next steps in a further blog post.

One thing that’s hidden away towards the end of the Committee agenda, but which makes for very interesting reading, is some correspondence between Transport Committee chair Mike Lee and NZTA State Highways Manager for Auckland Tommy Parker – in relation to spending, congestion and traffic volumes on Auckland’s state highway network over the past few years.

It all came from a presentation Tommy Parker did to the Transport Committee last month, after which Mike Lee sent a letter asking for a bit more information on a few matters. The questions he asked are outlined below:Tommy Parker’s response makes for interesting reading, as it includes some information that we’ve generally only been able to guess up until now.

In terms of capital works spending, as you can see from the table below the amount of money being spent on motorways in Auckland (remember this excludes operational spending on things like maintenance) has increased dramatically in recent years. In the 2010/2011 year over $600 million is being spent: the equivalent of the entire Project DART rail upgrade.Despite the massive increase in spending on state highways, it seems that congestion has only got worse over the past few years – although NZTA (probably correctly to an extent) attribute much of that trend to the disruption from roadworks associated with projects like the Newmarket Viaduct Replacement and the Victoria Park Tunnel:

The data on traffic volumes is a little more difficult to interpret, because it seems the methodology and the source of the information changed halfway through the period being measured – resulting in the last six months of 2008 being excluded from the data (my cynical side suggest that’s because traffic volumes plummeted then):The figures above somewhat contrast with much lower levels of increase on the “main motorway routes” over the past three years. I imagine the extensions to State Highway 20 over the past few years have led to volume increases there. Splitting traffic patterns on the motorway network into three zones: inner, middle and outer, produces some further interesting results:Mr Parker’s response also looks at the correlation between petrol prices and traffic volumes:

While he then goes on to note that over the past decade volumes have generally increased despite a doubling in petrol prices, personally I think he misses the point that the rate of increase in traffic levels is far slower than it has generally been historically. Furthermore, most of the data obviously doesn’t yet show what has happened to traffic volumes most recently – when petrol prices spiked over $2 a litre in the last couple of months. The previous time that happened, in 2008, volumes declined dramatically.

I suppose regardless of how you interpret the figures, it’s certainly useful for us to have a clearer picture of what’s going on with traffic volumes, state highway spending, congestion and so forth on our motorways. From my interpretation, it certainly seems a bit strange that we’re spending over half a billion dollars a year expanding a motorway network that has fairly static traffic volumes, and when the megabucks spent in recent years doesn’t seem to have done anything to alleviate congestion.

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