This is the second in a series of posts based on the Campaign for Better Transport’s submission to the Puhoi to Warkworth Board of Inquiry. The full presentation is over at bettertransport.org.nz
Yesterday I talked about the growth assumptions that lie behind NZTA’s traffic forecast for the Puhoi to North Warkworth Toll Road. (Because I think this a more accurate name for the project, I’m going to refer to it as the PNWTR).
In this post we are going to examine how NZTA have modelled the effect of the toll on projected traffic. The following chart is taken from the NZTA Traffic Assessment Report and shows predicted Annual Average Daily Traffic (AADT) volumes in both directions.
The two columns on the left indicate the expected change in traffic between 2009 and 2026 if the Base Case (“do nothing”) option is chosen. These are the same figures as the chart that appeared on yesterday’s post.
The three columns on the right are the predicted 2026 traffic volumes should the PNWTR proceed.
The 2026 PNWTR Corridor Total figure is higher than the 2026 Base Case figure because the authors of the report “assumed that the operation of the Project will increase growth rates in the study area [and therefore] we assumed that an extra 1% of traffic growth in the Project scenario is a reasonable approximation of the induced traffic effects of the Project” (p.13). In other words the 2026 PNWTR model has an underlying growth rate of 5.4%.
You can see from the chart that NZTA expect 13,700 veh/day on the PNWTR route, and volumes on the existing SH1 to be roughly the same as what they are today should the project proceed. ( As noted yesterday, I have yet to reconcile how the figure of 13,700 veh/day on the PNWTR with the 5,930 veh/day for trips “further north”.)
Obviously though the split of traffic will be dependent on the toll. The report doesn’t explicitly say what the assumption is on the toll tariff, but buried on p.59 is this:
Translated, (and later explicity clarified with NZTA) this means that travel on the PNWTR extension of the existing toll road is assumed to be free.
In reality, however, NZTA acknowledge that:
- The PNWTR road will be classified as a toll road
- No decision on the quantum of the toll has been made
- If a toll was applied to the Project, depending on the level of that toll there would likely be a reduction in traffic on the new project route and a corresponding increase in traffic on the existing state highway
It would be extraordinary to classify the road as a toll road and then not charge a toll for its use. It would seem prudent to do some scenario analysis to find out what the impacts on traffic volumes would be. The risk is that the PNWTR ends up being like one of Portugal’s Ghost Roads, while traffic volumes on the existing SH1 will be far greater than the NZTA modelling suggests.
As I said to the BOI:
The importance of a realistic forecast cannot be overstated. The proposed toll road will most likely be with us for hundreds of years, along with the significant environmental impacts that come with its construction and operation. A realistic forecast that has considered all relevant scenarios is vital, and it is worth spending some time and effort making sure we get it right.
I’ve run out of time, so I’ll cover off the forecast traffic volumes for Matakana in a future post, along with other shortcomings with NZTA’s forecasting, before moving on to the issues of economics, saftey and consideration of alternatives.