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Roading in Northland

There’s been quite a bit of discussion in the last week about roads in Northland following storm damage that saw part of State Highway 1 closed due to large washout. The severity of the slip saw traffic diverted on lengthy detours on roads clearly not designed to handle more than a handful of cars per day. Another series of slips have happened in the last few days, this time closing SH1 over the Brynderwyn Hills.

Understandably it’s led to people in Northland saying that their roads simply aren’t up to the same quality as roads in other regions. Oddly though it also led to Labour’s Kelvin Davis saying he supported the the Puhoi to Wellsford Road of National Significance.

“They want a safe and solid highway that’s going to get our people and goods in and out and that’s not at the whim of Mother Nature.

“This weather event has shown how vulnerable and susceptible the North is and it’s really important that we have a road where emergency services and whatever can get through, but also we’ve got to have a road that’s going to be able to export our produce outside of Northland and one that’s not going to be washed away in the next storm or flood.”

If the statement above was to be a blanket statement and not referring to P2W then I would be in complete agreement however I say it’s odd for him to bring up P2W as doesn’t even leave Auckland and would not have done anything to help with the slips that have occurred. In fact in many ways P2W is actually likely to be working against Northland as it will suck up funding that could be being used for widespread upgrades to address issues that exist in the roading network.

All up P2W is said to cost ~$1.6 billion with the first section to Warkworth estimated at $760 million. If the goal is truly about helping the Northland economy as the government love to claim then we need to be asking what else we could do with the money. What if we spent ~$300m on operation lifesaver to address the key issues with the existing road. We could then spend about $500 million on actual roads in Northland while still leaving up to $800 million which could be used for other projects – like part of the governments share of the City Rail Link.

But how would $500 million compare to what’s currently spent in the region and is it a significant enough amount of money?

Data from the NZTA can help to answer that question. Unfortunately the 2013/14 data isn’t available yet but this is for the 10 years to 30 June 2013.

Transport Spending in Northland 2003/04 to 2012/13 NZTA Local Authorities Total
State Highways – New and Improved $163,617,783 $163,617,783
State Highways – Maintenance, Operations & Renewals $249,305,778 $249,305,778
Local Roads – New and Improved $174,917,159 $56,850,123 $231,767,282
Local Roads – Maintenance, Operations & Renewals $312,908,053 $226,434,207 $539,342,260
Public Transport $9,481,230 $8,440,738 $17,921,968
Walking & cycling $342,494 $90,300 $432,794
Other $24,816,399 $2,661,551 $27,477,950
Total $935,388,896 $294,476,919 $1,229,865,815

And here’s the new and improved road spending over that 10 year periodNorthland New and Improved Roads Spending

So spending $500 million (on top of what would normally be spent) would be more than all the money that was spent on new and improved state highways and local roads for over a decade.

That seems like it could deliver more game changing outcomes for transport in Northland than a motorway to Warkworth/Wellsford ever would. As an example of what might be able to be delivered, the governments Accelerated Regional Roading Package named two projects that would see road realignments happen. One was on State Highway 73 near Arthurs Pass and the other was just south where the large slip occurred the other week with the project known as the Akerama Curves Realignment and Passing Lane. The latter is a 3km section of road that will be upgraded and have an additional passing lane added for a cost of $10-13.5 million. Comparing the costs for each project it suggests that for $500 million we could probably get 100-150km of upgraded state highway which is a substantial amount.

I guess the big problem with this suggestion is that small scale projects like road realignment and passing lanes aren’t the types of projects that get politicians in the national media cutting turning a first sod or cutting a ribbon.

Puhoi Warkworth Hearing Finishes Today

This is the seventh in a series of posts based on the Campaign for Better Transport’s submission to the Puhoi to Warkworth Board of Inquiry

The Board of Inquiry Hearing into the Puhoi Warkworth toll road was meant to finish last week, however NZTA are giving their closing submission today (Thursday 5th June) at Courtroom 2.01, Level 2 Chorus Building, 42 Federal St, from 10am.

The CBT was permitted to submit a written closing submission, which we did so on Wednesday of last week.

On Friday of the previous week, we were given permission to cross examine the NZTA’s traffic expert on the significant issues we have raised here in previous posts. You can read the full transcript yourself, but in general all of the points made in previous posts on the blog were confirmed, including traffic modelling being based on no toll tariff for the toll road.  Of course, in spite of all the inconsistencies with the traffic evidence, the NZTA still conclude that “No expert traffic evidence has been called to dispute the evidence”, and the Board haven’t been of a mind to appoint any experts of their own to advise them, as has been the case in the Basin Reserve Board of Inquiry.

To help with the legal aspects of our submission, the CBT engaged the services of Rob Enright, a former RMA solicitor now acting as a barrister, to write a closing legal submission. Rob had recent success on behalf of the Environmental Defence Society in the Supreme Court.  There is a lot for the Board to consider in the legal submission, but as Rob says:

Perhaps CBT’s strongest point is that the NZTA has failed to undertake a cost-benefit analysis of the relative merits of the proposed designation, despite this being commonplace for NZTA projects.

Remember, the proposed toll road is just 700m shorter than the existing route. At most, just 3 minutes will be shaved off current journey times.  For trips to Warkworth and the Matakana beaches, travel time savings are likely to be zero. It will be interesting to see how the Board and NZTA respond to the legal points Rob has made.

So the following issues remain in contention for the CBT:

1. Whether projected traffic volumes for the Project route and existing SH1 are realistic
2. Whether a supporting economic analysis consistent with the NZTA’s Economic Evaluation Manual should be supplied
3. Whether alternatives have been adequately considered
4. Whether unsafe sections of the existing SH1 require mitigation

We’ve covered all but the last of these issues in previous posts , so the remainder of this post focuses on the safety of the existing SH1, and comes from our closing submission.

The  Traffic Report 2026 Project case forecasts that the existing SH1 will remain three times as dangerous as the toll road, as illustrated here with the 3rd and 4th columns of this bar chart:

forecast injury crashes


The overall forecast reduction in accidents (23%) is only achieved if the forecast reduction in traffic on the existing SH1 eventuates.

In Section 2.4 Effect of Traffic Report Assumptions of our closing submission, we identified the potential for an increase in traffic on the 2026 existing SH1 of between 5,089 and 7,027 vehicles a day, primarily due to the effect of tolling.

Since accident rates are assumed to be in proportion to traffic, the forecast reduction in accidents will not occur if more traffic is on the relatively unsafe SH1.

In addition, we believe this could mean that the overall accident rate on the corridor between Puhoi and Wellsford will not improve as a result of the Project, as with current modelling there is only a small improvement in annual injury accidents forecast. More traffic on SH1 would potentially eliminate this slight improvement.

The Traffic Report considers future accident rates on the Project toll road and the existing SH1, and states :

The average annual number of injury crashes in the corridor is forecast to decrease by five (23%) in the year 2026 in comparison to the future traffic volumes on the existing SH1 route.

Modelling crash rates in the entire corridor, including the existing SH1, is the correct approach.

But it is unclear why a 23% improvement is an acceptable figure. It should not become a defacto target. Accident rates could be lower if further improvements to the existing SH1 were undertaken.

The Traffic Report identifies a number of accident black spots. For instance :

The 1.6km section of road between Valerie Close and McKinney Road has had the most serious and fatal crashes. The one fatal pedestrian crash was within this section approximately 160m north of the SH1 and Toovey Road intersection.

To remedy this is estimated to cost $2.9m, with a BCR of 2.1. (Costs and BCRs come from this OIA document.)

Schedewys Hill has a particularly poor horizontal and vertical alignment with two passing lanes on curves that terminate near bends. This geometry has resulted in a large number of minor injury accidents on this relatively short section of SH1.

To remedy this was estimated to cost between $25.8m and $70m in 2002, with a BCR of between 1.3 and 1.4.

Similarly, the Pohuehue Viaduct can be made safer for a cost of just $4.7m (2006), with a high BCR of 3.2.

It seems perverse that the NZTA will entertain spending millions of dollars in order to minimise the removal of the Kauri trees across the project area , and yet will not spend any money to provide for the additional health and safety of people and communities. Environmental mitigation is important, but the safety of people and communities should be even more so.

The fact that the NZTA has chosen a Project alignment outside of the current SH1 alignment should not exonerate the NZTA from making these safety improvements, particularly as positive BCRs have already been calculated.

A draft decision from the Board is due in late July

A Better Alternative for Puhoi to Warkworth (And How to Save Half a Billion Dollars)

This is the sixth 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

In this post we take a look at what alternatives to the NZ Transport Agency’s $760m Puhoi to North Warkworth toll road have been considered.

Operation Lifesaver

It should come as no surprise to regular readers that our preferred solution is Operation Lifesaver, which is a bypass of Warkworth and upgrades of the existing route.

Design, construction and cost estimates for this were based on the NZTA’s own cost estimates.  Right up until 2008, the NZTA’s preferred option was to upgrade the existing alignment.  Luke Christensen discovered that the 2008 NLTP had $3.6m set aside for investigations into a Schedewys Hill deviation, of which $500k was actually spent.

Originally the scope of Operation Lifesaver included improvements to the Warkworth to Wellsford section of the highway, but the key improvements for the Puhoi  to Warkworth section are:

  • A bypass of Warkworth
  • Pohuehue Viaduct widening and safety improvements
  • Schedewys Hill
  • Safety upgrades

A bypass of Warkworth could be built largely within the northern part of the proposed designation:

Warkworth Bypass. NZTA proposed designation shown in red.

Warkworth Bypass. NZTA proposed designation shown in red.

Construction of the Warkworth bypass would avoid the significant environmental damage that will occur south of Perry Road if the toll road proceeds. The blue line is a new link road, and its exact position would need to be determined in consultation with residents. (Significant growth is planned for the southern part of Warkworth around Valerie Close, which is the side road north of Perry Rd on the map.)

The green line is the Matakana link road.  Without this link road, congestion at Warkworth will get significantly worse as all traffic to or from Matakana or Snells beach is forced through the Hill Street intersection.  NZTA’s proposed toll road does not include this link road.

The cost of this bypass would be similar to the 7 Km Mangatawhiri Bypass, which involved over 2,000m of culverts and ended up costing $43m all up.

Pohuehue Viaduct widening and a deviation of Schedeways Hill was covered in a 2010 response to an OIA request made by the CBT.

  • The preferred option for the Pohuehue Viaduct in 2006 was to widen it to two southbound lanes and one northbound lane, as well as upgrade the edge protection to a barrier that complies with NZTA’s standards. This was costed at $4.7m in 2006 and had a BCR of 3.2
  • Three options were investigated in 2002 for a deviation at Schedeways Hill, ranging in cost from $25.8m to $70m, with BCRs of 1.3 or 1.4.  All of these options involved a direct alignment that would cut through the ridge. (No word on the outcome of the $500k spent in 2008.)
  • In the same OIA response, a passing lane just south of Warkworth was also investigated and costed at $2.9m with a BCR of 2.1. The NZTA say this option was taken through to scheme assessment stage but was terminated following opposition from the then Rodney district council.

So all up the cost of these changes comes to $120.6m, but to be on the safe side we could double the estimate to $240m, and it would still be $520m cheaper than the NZTA’s toll road option.

To recap, this is a better alternative because:

  • Environmental impacts are minimised. There is no risk of damage to the Puhoi estuary from sediment flows, and hundreds of kauri trees will be saved.  Land owners south of Perry Road get to keep their farms intact and can continue to live in their houses.
  • At least half a billion dollars can be saved, meaning either less petrol and RUC taxes, or spending the money on more worthwhile projects such as safety upgrades in the Dome Valley or further north.
  • Construction traffic will be far less than that predicted for NZTA’s toll road
  • Work can be staged and will most likely be completed before NZTA’s forecast completion date for the toll road of 2021.
  • All users of the corridor benefit from SH1 alignment and safety upgrades. Remember at the completion of the toll road, traffic volumes on the existing SH1 will be similar, if not more, than they are today.

NZTA’s Response

In their rebuttal evidence, this is what the NZTA had to say on the Puhoi to Warkworth components of OperationLifesaver:

My assessment of the CBT options from a design and construction perspective is that they have not been adequately scoped and CBT has not considered appropriately the practical difficulties of their construction (and hence their cost).

By way of example, the route through Schedewys Hill is narrow and winding. Introducing a central median barrier would require additional road width for the barrier and an appropriate central median. Similarly, a side protection barrier would require additional shoulder width in front of the barrier in order to provide for traffic to pass stopped/ broken down vehicles. Creating this extra carriageway width would be extremely expensive and difficult to achieve, with the likelihood that extensive retaining wall construction and slope protection works would be needed in geologically unstable terrain. Additionally, the difficulties of achieving such construction in a safe manner, for both the construction workforce and motorists, would be immense. As a consequence, the cost of implementing these suggested works would in my opinion be many times that suggested in the CBT document.

The CBT document also advocates the SHl upgrade alternatives as being able to be delivered much sooner than the Project. However, the options for such works would need appropriate assessment, particularly in respect of a Warkworth bypass and any realignment at Schedewys Hill. The Transport Agency would need to obtain a new and/or widened designation and appropriate resource consent. Construction, particularly of the ‘on line’ works, would be extremely disruptive to existing traffic flows, would require multiple phase-traffic management measures and would result in a very inefficient (ie slow and costly) construction methodology and programme. From experience, I would anticipate that the necessary time period from inception of the assessment process, through to completion of the works could easily be of the order of 6-7 years.

Upon completion of the proposed upgrades,SHl would continue to suffer many of the issues currently associated with its operation, and its ability to address future traffic growth and assist economic development would be little changed. It would remain the only through route between Puhoi and Warkworth and, as such, the resilience of the State highway network to major natural events or accidents would be unchanged.

Having considered the above, it is my opinion that the CBT SHl upgrade proposals overall, as an alternative to the Project, are ill conceived and do not represent a viable option. Moreover, CBT’s assessments of the likely cost of such works are at best questionable, and I would expect actual costs to be many multiples of the CBT estimates. This expenditure would then need to be considered in light of the extent to which these upgrades meet the Project objectives. In this respect, it is my view that the overall performance of the SHl upgrades as proposed by CBT, is significantly inferior to that achieved by the Project.

At no point do the NZTA define what is meant by “overall performance”. NZTA have not carried out a benefit cost analysis for any option, including their own, let alone one that does not involve a four lane RoNS motorway standard. As discussed above, NZTA could get a very accurate handle on costs if they wanted to - they would just need to bring the costings that they have already done up to date.

The argument that construction will be disruptive to existing traffic flows understates NZTA’s recent successes.  The inline upgrade of the Newmarket viaduct, one of New Zealand’s busiest motorway sections, was achieved while being kept open, for the most part, to traffic.

Below the fold, I provide a bit of legal context to the consideration of alternatives.

Continue reading A Better Alternative for Puhoi to Warkworth (And How to Save Half a Billion Dollars)

No Economic Rationale for $760m Warkworth Toll Road

This is the fifth 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

In this post we look at the economic justification for the Puhoi to North Warkworth Toll Road (PNWTR).

In the executive summary of the Assessment of Environmental Effects (AEE), the NZ Transport Agency has provided the following table of economic effects:

Economic Summary from the AEE executive summary

Economic Summary from the AEE executive summary

While the NZTA assert that there are positive economic effects from the project, the only evidence supplied is a letter providing a high level assessment.  The letter contains general assertions such as “there will be improvements in the economic welfare for Auckland and Northland businesses and residents”, but no quantitative analysis is undertaken.

NZTA claim that the Project will lead to reductions in vehicle operating costs, yet travel time savings for many in the Warkworth and Matakana regions will be in the order of one or two minutes.  Tolls will add significantly to vehicle operating costs, so claiming vehicle operating costs will reduce is unsubstantiated.

No evidence-in-chief has been supplied to back up any of the positive economic effects claimed in the Executive Summary.

At the Board of Inquiry,  NZTA’s Tommy Parker said the idea of the PNWTR is to stimulate the economy in the north:

It is also important for the Board to know that this is seen as a lead infrastructure so the nature of the policy is to provide infrastructure that will stimulate economic growth in areas of economic potential, and that you will be aware that the two regions that will be affected by this project is New Zealand’s most prosperous region in Auckland and one of its least prosperous regions in Northland. So the idea is to connect the two, get greater connectivity between the two to stimulate the economy in the north.

The reality is there is no correlation between travel time savings and economic growth in Northland.  In March of this year, Statistics NZ published regional GDP figures. Here is the chart for Northland:

Northland GDP (source Statistics NZ)

Northland GDP (source Statistics NZ)


On 25th January 2009, the Northern Gateway Toll Road (NGTR) opened, offering a travel time saving of up to 9 minutes.  This is a far greater travel time saving than that offered by the PNWTR, so you would expect to see a corresponding increase in GDP for Northland if there is a linkage between road building and GDP.

You can see that immediately after opening, GDP in Northland dropped, before rebounding to the 2009 level.  There was clearly no correlation for the NGTR, so it is likely that the PNWTR, with smaller travel time savings, will also have no correlation with economic growth.

NZTA have not quantified how project travel time savings equate to economic benefit. Table 7 of the Traffic Assessment Report shows Northbound travel time savings:

Table 7: Northbound travel times in minutes

Table 7: Northbound travel times in minutes

The third column is headed up “2026 Project using fastest route”, because in the bottom three scenarios the fastest route is via SH1, not the toll road. The use of percentage figures gives the impression that travel time savings are significant. However, the travel time savings for the Warkworth, Woodcocks and Eastern Beaches routes are miniscule – just one or two minutes at most times of the day. (Ignorning HS and HE which stand for Holiday Start and Holiday End). It is unlikely that these travel time savings will equate to any meaningful economic benefits.

Here are the Southbound trips from Table 8:


Travel time savings are claimed to be greater, but the odd thing here is that this is because the base case travel times are so much more than for the north bound trips. No reason is given in the report for this.

It may be related, but there is a bit of an anomaly with the routes used determine travel times. The report says the 2026 Base Case assumes that the Western Collector will be completed. This is shown on the map below.

Warkworth Western Collector, forecast to be complete by 2021

Warkworth Western Collector, forecast to be complete by 2021

The Western Collector should offer travel time savings to Woodcocks and possibly to the North for trips on the existing SH1. However, looking at the travel time routes used for the 2026 scenarios, the Western Collector clearly isn’t used to determine the base case numbers above.

Figure 15: 2026 Travel time routes of the Transportation Assessment Report

Figure 15: 2026 Travel time routes of the Transportation Assessment Report

Instead of turning opposite McKinney Rd, trips to and from Woodcocks are modelled to take the long route. This will be overstating the Base Case travel times for trips to the Woodcocks area and possibly to / from the North as well.

Contrast the complete lack of economic evidence for the PNWTR with the evidence-in-chief supplied for the Basin Reserve Board of Inquiry. Here is what NZTA’s economist has to say about that project:

From Basin Reserve BOI Evidence In Chief

From Basin Reserve BOI Evidence In Chief

NZTA acknowledge that economics are relevant considerations under the RMA for the Basin Reserve Flyover, but apparently this is not the case for the PNWTR. You could argue that a Benefit Cost Ratio of 1.2 is hardly a ringing endorsement of the economic worth of the Basin Reserve flyover, but at least NZTA have bothered to carry out some kind of calculation of the benefits of travel time savings, vehicle operating cost savings and so on against the cost of the project. Presumably the economics of the PNWTR are so bad that NZTA would rather not provide an economic assessment at all. NZTA should not be able to pick and choose which projects they provide an economic business case for, and which they do not.

Bear in mind that the discussion of economics at the Board of Inquiry takes place in the context of the Resource Management Act.  Commissioner Chandler made the following comment at the hearing on the 10th April:

MR CHANDLER: Perhaps I’ll just mention, Mr Pitches, talking about cost benefit ratios, the Board of course cannot take cost benefit ratios into account in its decision making.

MR PITCHES: All right. So just to respond to that. Benefit cost ratios generally are an indicator of the economic worth of the project, which is why I included it in my presentation. I still stand by my statement that the Resource Management Act place weight upon the economic value of the proposed project and should be considered.

To me it seems ludicrous that the Board should not consider the economic worth of the project, as measured through a benefit cost ratio.  If the NZTA were proposing a 32 lane motorway then surely a Board of Inquiry would be obliged to test the economic rationale. But then again I’m not an RMA lawyer.

Perhaps it comes down to how adequately the NZTA have considered alternatives.  I will be covering this in my next post.

Mahurangi Matters on the Puhoi Warkworth Board of Inquiry

To date there has been limited media coverage on the Puhoi Warkworth Board of Inquiry.

Fortunately Karyn Scherer, from the local Warkworth newspaper Mahurangi Matters, is one of the few reporters attending the BoI.  She writes in her opinion piece:

As someone who lives not too far north of where the Puhoi to Warkworth motorway is likely to terminate (or originate), I should be eagerly awaiting its completion.  I travel to Auckland fairly regularly and I have to confess I rather enjoy slipping my sedan into cruise control once I hit the Northern Gateway, and cranking up the stereo.

This is the thinking of most of the general public I think.  Perhaps it explains why there hasn’t been much media coverage – the promise of the freedom of the open road, unimpeded by others means that few are able to conceive the construction of the toll road will be anything but a good thing.  Others may buy into the NZTA argument that this is “lead infrastructure”, and even though the capacity isn’t required now, there will come a time when it is. Ms Scherer continues:

But even before this month’s public hearing into the motorway extension began, I was starting to have doubts about whether it was a good idea.

Meeting some of the people whose lives have already been destroyed by the proposal because they live along the route was more than just food for thought. Sure, you need to crack a few eggs in order to make an omelette, but shouldn’t we also consider whether too many omelettes will give us a heart attack one day?

The most sense I have heard so far in the hearing was from the Campaign for Better Transport, a voluntary organisation of about 50 people that has won some important battles over transport issues. The elephant in the room at the country lodge in Silverdale where the hearing is taking place is the economic rationale for the project. Basically, there isn’t one. It’s a political decision, driven largely, I suspect, by the Government’s desire to spend up on infrastructure to help stimulate the economy in the wake of the GFC.

Bingo! Ms Scherer is a former business reporter at the Herald.

The problem with such Keynesian responses is that there is a long-term price to be paid.

I’m well aware that most people in this area want the new motorway – but few seem to have given much thought as to who will pay for it, and whether it is worth it. There is no such thing as a free motorway, so ultimately it will be taxpayers who fit the bill, and those who pay the tolls.

Those who can’t afford the tolls will miss out on its benefits. Ironically, they are likely to be commuters who travel to Auckland for work, and could do with a decent motorway. For much less than $760 million, says the CBT, we could upgrade the existing highway and everyone would benefit.

Read what the CBT has to say in this transcript. It starts at page 382.

At last, some commentary on the fact that this will be a toll road, and the fact that there is no economic business case behind it.  Because the northern junction of the project is almost two kilometres to the north of Warkworth’s main intersection, there is a high probability that many Warkworth and Matakana residents aren’t actually going to use the new route, especially if it is tolled.

The transcript linked to in the editorial relates to the presentation I gave to the Board on the 9th of April. My appearance was supposed to be at 11:00am, however I wasn’t called until 4:30pm by which time any media had gone home.

The following day I was sworn in and cross-examined by the NZTA and the Board for 40 minutes. I think this transcript (from page 412) is more revealing of the Board’s thinking.  I’ve put the highlights below the fold to stop this post from getting too lengthy.

Continue reading Mahurangi Matters on the Puhoi Warkworth Board of Inquiry

Low Traffic Forecast For Costly Warkworth Toll Road

This is the fourth 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

Previously I pointed out that the NZTA produced Traffic Assessment Report for the Puhoi to North Warkworth Toll Road (PNWTR) is not realistic in a number of areas:

It is very hard to appreciate the significant combined effect of these erroneous assumptions, so I’ve modelled the outcome in this table:

Projected Puhoi To North Warkworth Toll Road Traffic Volumes for 2026

Projected Puhoi To North Warkworth Toll Road Traffic Volumes for 2026

The more realistic input assumptions mean the result is 56% less traffic on the toll road, and 50% more on the existing SH1 than NZTA’s forecast.

This is significant, not just because 6,031 really is a pitiful amount of traffic for a $760m toll road, but because one of the objectives of the toll road is to reduce congestion at Warkworth.  Current AADT volumes are about 17,400 veh/day, so traffic volumes of 21,788 represent an increase in traffic volumes of 25% by 2026 on the existing SH1.  Without improvements to Hill St, delays will get far worse after the project is completed. It also means the claimed safety benefits are doubtful. There aren’t any safety improvements proposed for the existing SH1, so the number of accidents will be higher than NZTA’s report also. I’ll be talking more about this in a subsequent post.

The assumptions that I have used are laid out here:


Stepping through each assumption:

  • Project scenario straight line growth.  Although the NZTA’s own Economic Evaluation Manual stipulates a zero default growth rate should be used, I have based growth on the historic trend of 2.1%. Incidentally if you use a higher growth rate than this, more traffic results on SH1.
  • Toll route % traffic: This is the split of traffic assumed without a toll. I’ve simply used the same split identified in the original report.
  • Warkworth Plan Increase in SH1: The 2,800 increase in traffic on SH1 comes from Test B of the original report.  I’m assuming this because most new growth is currently planned to be in the west and south of Warkworth. Obviously if there is an increase in traffic on SH1, there must also be a reduction in traffic from the toll road.
  • Matakana straight line growth: The original report assumed virtually nil growth, but here I’ve assumed the same growth for Matakana Road as for Sandspit Rd.  I’ve assumed 50% of the additional Matakana traffic will take the toll road. The 50/50 split is roughly the split the original report claimed. Although NZTA have since retracted this split, I’ll run with this for now.
  • Toll diversion: The effect of any toll is to divert traffic on to the free alternative. I haven’t modelled a toll tariff amount, I’ve simply assumed that the NZTA will set a toll that will divert about 15% of the “further north” traffic and 80% of traffic to Warkworth and the eastern beaches.  There is a greater diversion of traffic for these destinations as the existing SH1 is already forecast to be quicker.  I’m just assuming 20% of these trips will be on the toll road because of the increased safety and comfort of the toll road, even though the trip will take longer. (Off memory, about 25% of trips on the Northern Gateway corridor takes the free the Hibiscus Coast route.)

So there you have it. You can test your own assumptions by downloading the spreadsheet.

NZTA Predict No Growth For Matakana

This is the third 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

Previously I pointed out that the NZTA produced Traffic Assessment Report hasn’t factored in a toll for the Puhoi to North Warkworth Toll Road (PNWTR), thus overstating expected volumes on the proposed route. Before that I made the case that traffic growth assumptions for the corridor aren’t based on current trends, and that the forecast number of trips “further north” was overstated in the report to the Board of Inquiry.

In this post I examine NZTA’s forecast growth in traffic for the Matakana region and Warkworth.  Matakana Road is the route to the Omaha, Leigh, Goat Island and numerous other coastal destinations. These destinations are very popular during weekends and holiday periods.

Here’s the 2009 Base Case traffic counts taken from figure 11 of the report:

Base Case 2009 AADT volumes

Base Case 2009 AADT volumes

And here are the 2026 traffic volumes predicted by NZTA’s model:

2026 AADT Volumes

2026 AADT Volumes

As you can see, the model predicts Matakana traffic volumes to increase by only 500 for the Base Case in 2026, and by 700 for the Project Case.

In my view this is highly unlikely.  The model even predicts south bound traffic volumes to decrease by 20 trips a day for the “Holiday End” periods for the Base Case, and remain the same for the Project Case.  In my experience, the ends of long weekends and holidays are the busiest times on Matakana Road.  The implied growth of 0.3% per annum in AADT traffic volumes does not make sense, especially when you consider the number of new dwellings that will probably be built in the Matakana region in the next 17 years by 2026.   If this is the same assumption used to model the Hill Street intersection, then delays are likely going to be far greater in reality than forecast.

It is even more odd when you compare the Matakana Road growth assumption with that used for Sandspit Road, which connects to Snell’s beach and the Mahurangi peninsula.  Those figures work out to be a linear growth of 2.9% for the Base Case and 3.0% for the Project Case, which is more in line with what one would expect.

The land use assumptions are on pages 8,  13 and 14 of the report. For the Base Case and Project Case, this includes land-use changes (growth) in Warkworth.  For the Project Case, the following adjustment was made:


So even though it isn’t in the Warkworth Structure Plan (or the Unitary Plan?), the growth has been modelled to take place near the northern junction of the PNWTR. To the author’s credit there was a sensitivity test done on this assumption:

test b

So 20% more traffic on the existing SH1 for the more likely growth scenario, than shown in the main body of the report!  So instead of 14,500 veh/day, traffic volumes on the existing SH1 are more likely 17,300. And presumably 2,800 veh/day less on the toll road.   No wonder it is buried at the end of the report.

My next post will cover one final traffic modelling issue, before moving on to the topics of economics, safety and consideration of alternative routes.

NZTA’s Traffic Assessment for Puhoi to Warkworth

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

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:

Northern Intersection Revised Cropped

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.


Hill Street Blues

We’ve discussed Warkworth’s notorious Hill St intersection previously, but it seems timely to revisit again with the Board of Inquiry underway on the Puhoi – Warkworth toll road and NZTA’s recent press release on the subject:

The NZ Transport Agency says its priority to improve traffic flows in the Warkworth area is to first construct a new highway between Puhoi and Warkworth before it upgrades the community’s Hill Street intersection.

“I acknowledge that many in the community want Hill Street upgraded as soon as possible, but it is important that we have a reliable alternative route in place first for people before we tackle Hill Street,” says the Transport Agency’s State Highway Manager, Tommy Parker.

Mr Parker says upgrading the intersection and the state highway and five local roads that feed into it will be a complex task that will take some time to complete.

“There’s not a lot of room at the intersection and we will need to keep all those roads open during the upgrade. We estimate construction could take two summers to complete and that will mean considerable disruption for everyone – children from the nearby school, residents, local businesses and road users.

“Upgrading Hill Street, either in isolation or ahead of the new highway, will not provide substantial relief from congestion. It makes sense to construct the highway first to help us manage the disruption from that work and divert traffic away from the intersection.”

Before analysing NZTA’s announcement in more detail, here is a map of the current intersection:

Hill St Map

And the GIS view:

Hill St GIS

As you can imagine, the intersection turns into a real bottleneck at peak times, particularly in the summer months.

Traffic from Warkworth village heading to Matakana must turn right at a give way sign, across a lane of queued traffic, giving way to traffic from a number of directions concurrently. Traffic queues across the intersection can often block other traffic movements in other directions. In summary, it is a real mess.

Further down in their press release, NZTA mention a couple of other projects:

Mr Parker says the Transport Agency is working with Auckland Transport – Auckland Council’s transport body – to progress other options including the Matakana Link, which will connect with the new highway and bypass Hill Street to the region’s eastern beaches, the Western Collector in the town and the SH1/McKinney Road intersection south of the township.

Firstly, looking at the Western Collector:


This is an AT sponsored project which is a complete bypass around Hill Street and central Warkworth. It starts at opposite McKinney Road in the south and ends at Hudson Road north of Hill Street. Anyone heading to or from the north on the existing SH1 will certainly use this, reducing pressure on Hill St. A number of intersections that make up the bypass have already been completed, but I can’t find any information via Google on when the missing links will be completed. It is supposed to happen before the Puhoi – Warkworth toll road, however.

Secondly, the Matakana Link is mentioned, crudely highlighted in blue on the map below. At this stage this is unfunded and does not form part of the Puhoi – Warkworth toll road project. However, without it the toll road will be useless for people wanting to travel to or from the Matakana area.

As currently scoped, the toll road will join 1.8 km north of the Hill Street intersection. Anyone travelling to Matakana on the new toll road will have to cover an extra 3 km at least to get to Hill Street, compared to using the existing SH1.

Puhoi Warkworth Northern Junction

So are NZTA right in delaying Hill Street by at least another 10 years? On the one hand, the scale of any new intersection could be reduced because of the Western Collector and the possibility of the Matakana link.

On the other hand, for Warkworth residents this is a long time to wait, so why not start now? Remember also that Warkworth residents won’t directly benefit from the new toll road either, as the fastest route south will still be the existing SH1, so they seem to be getting a rough deal from the announcement.

Photo of the day – Alpurt

A few questions:

Does this motorway really need to be extended all the way to Warkworth?

Does anyone ever drive at the speed limit on this stretch of motorway?


Photo is credited to