This is the first 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 can be found over at bettertransport.org.nz
In this post we take a closer look at the Transportation and Traffic Assessment Report which the NZTA have supplied in support of their application for a $760m toll road from Puhoi to north Warkworth. In particular, we will examine the forecast traffic growth and volumes “further north”.
NZTA have modelled traffic growth at a rate of 4.4% per annum (straight line) until 2026. This is the forecast growth without the toll road, explained on p.27:
As you can see, NZTA claim that the 4.4% growth figure is “consistent with the growth rate observed over the last five years which has averaged 4.1%.”
Footnote 21 says the 4.1% figure is based on NZTA’s TMS count site south of McKinney Road, which is just south of central Warkworth. Looking at the data from the NZTA State Highway Traffic Volumes, a growth rate of 4% does indeed appear to be not a bad fit. The figures quoted are two way traffic counts.
However, the report does not explain why this particular count site has been chosen. Traffic counts at McKinney Road will reflect the growth of trips in and around Warkworth itself – trips that aren’t necessarily travelling long distances at all.
It would therefore make more sense to consider the number of vehicles that currently travel the whole distance from Puhoi to Wellsford and beyond every day, and vice versa – what I will refer to as “further north” trips. We can get an idea of the trend in this traffic by looking at Kaipara Flats road, which is just north of the northern junction of the project.
As you can see, this chart tells a very different story – no long term growth whatsoever for the period 2008 to 2012. Other traffic counters like the one at Waipu show a similar “flatline” trend.
But at this point we still don’t know what proportion of these trips are “further north”. I asked NZTA if they had modelled “further north” trips and it turns out they had, but hadn’t included it in the report.
The 2009 Base Case model comes out at just 4,460 trips a day. The 2026 Project model, 5 years after the project is complete, has 5,930 trips travelling to or from “further north”.
This seems like an astonishingly small number of trips for which to build a four lane toll road. NZTA claim that a number of toll road users will have origins or destinations in Warkworth and Matakana, despite the fact that it will be quicker to use the existing SH1.
NZTA originally provided a projected split of toll road traffic at the northern junction as 10,500 travelling to/from the north and 12,100 travelling to/from Warkworth, as shown in the following diagram:
However, along with supplying the “further north” figures, they have also supplied a new diagram for the toll road split, which looks like this:
Go figure. Apparently NZTA are no longer sure what the split in traffic will be. Without this, trying to get a handle on expected traffic flows becomes hard. If we know only 5,930 trips are travelling to / from “further north”, then this represents only 31% of the traffic north of Kaipara Flats (19,200). Where are all the other vehicles coming from, and what impact will the proposed toll road have on their travel times? I’m hoping NZTA will be providing the revised split of traffic or, ideally, the whole report will be subject to an independent review.
In the next post I will discuss NZTA’s forecast traffic volumes for Matakana, and why the forecast of 14,000 vehicles a day for the new toll road may be way overstated. (Hint: it is to do with the toll.)
Thanks to mfwic in the comments below, we have an extended series of data for McKinney Rd. With a base line of 2003, linear growth of just 2.1% is observed. Which makes NZTA’s modelling look even more overstated.