There has been surprisingly little criticism of the Auckland Transport Alignment Project so far. One of the the only ones has been about the plan to build Penlink as a two lane road instead of four lanes. For example, the CEO of the National Road Carriers, David Atkin said:
Mr Aitken said the projects need to be future proofed now. “By the time Penlink is built the two lanes won’t be adequate, so they might as well build the four lanes straight away.”
While Stephen Selwood of Infrastructure NZ said:
“First, underinvestment in capacity to meet foreseeable demand must stop. A fourth main trunk rail line will be required in the future, as will four lanes on the Penlink corridor and the extension of the Mill Rd corridor. These investments open up land for housing, have positive economic benefits and should be front-footed, not reacted to when capacity is exhausted.
To assess if they’re right, we first need to answer two questions
- Does Penlink need to be four lanes, now or in the future
- Should we build all four lanes now
So let’s look at those
Does Penlink need to be four lanes, now or in the future
For most of it’s life, Penlink was considered as just a two lane road and was designated as such. Only in about 2015 did Auckland Transport decide to change that to four lanes as well as grade separating some of the local connections to the new road.
ATAP says this about Penlink and the decision for two lanes.
Transport modelling suggests that with a toll in place, Penlink has sufficient capacity as a two-lane road to meet foreseeable future demand, although it will be designed in such a way that it is future proofed for four lanes.
This doesn’t give us too much, luckily there is plenty of other information available in the public domain. A recent update to the Hibiscus Local Board confirms how many people are expected to use the new road, both if it’s tolled or untolled. The government have already confirmed that the road will be tolled and the modelling suggests 11,800 vehicles would use it in 2026 and 16,800 vehicles in 2046.
You’ll notice there are two scenario’s listed (A & C). This relates to whether southbound on SH1 is widened or not however both options suggest similar usage.
So, do we need four lanes? We can relatively easily test this by looking at other roads carrying similar volumes or more volumes. I started by looking at Auckland Transport’s road count numbers and focused on the 5-day averages as they represent working days as opposed to including weekends in the results.
This revealed dozens upon dozens of streets that carry similar or more vehicles to what is expected of Penlink but on only two lanes. Some examples include
- Abbots Way, Remuera (Kenneth Small Pl to Ngahue Dr) – 24,800 per day
- Station Rd, Papatoetoe (Ashlynne Ave to Gray Ave) – 23,400 per day
- Universal Dr, Henderson (Meadowcroft Way to Lincoln Garden Pl) – 23,500 per day
- White Swan Rd (between Hillsborough Rd and Lynfield Pl) – 23,500 per day
As you will have noticed, these are all two lane roads capable of handling more traffic than what is expected in 2046 if there was no toll. There are plenty of State Highways that we could include in this too, for example SH16 south of Coatesville Riverhead Highway carries over 33,100 vehicles per day and there are no plans anytime soon to increase the capacity of that road.
Pure carrying capacity isn’t the only issue that needs to be considered though. What happens when Penlink gets to SH1 also needs to be factored in. Currently SH1 in this area in this area is two lanes each way and ATAP doesn’t allow for funding increasing this. Adding two lanes of traffic to a two-lane motorway isn’t going to result in anything but congestion, negating most of the time savings Penlink is supposed to provide.
Next we’ve got housing and Selwoods comment about Penlink needing to be four lanes to open up housing is a little disingenuous. The housing it is supply it is intended to open up isn’t on the peninsula but in and around Silverdale and is meant to do that by taking Peninsula vehicles out of the Silverdale motorway interchange to free up that space for the cars of the new houses that will be built.
The Unitary Plan doesn’t allow for much more development on the Peninsula, perhaps if locals want the road to be four lanes it should come with significant upzoning to support it.
It’s also worth remembering that this will be a toll road. One of the features of a toll road is that you can change the toll to control how many people use it. Selwood himself is one of the biggest advocates for motorway tolling. If two lanes were insufficient, we could just change the toll to manage demand.
Finally, the strongest argument for building four lanes seems to be that it provides the opportunity for bus or transit lanes. The benefit of this seems dubious as most likely these extra lanes would only be needed near each end of the road, and that should be relatively easy to provide. As per above, demand could be managed to ensure the rest of the route flows freely.
Unless the modelling is completely wrong, there doesn’t seem to be to be a good justification to make Penlink four lanes, now or in the future.
Should we build all four lanes now
I think we’ve established that four lanes really aren’t needed for Penlink, but just for the sake of argument we did at some point in the future, should we build all four now. There are about 100 million good reasons not to. The overall transport package might be $28 billion over the next decade but there is a long list of projects that didn’t yet make the cut and many of those would likely provide greater value than the net benefit of four-laning Penlink. As the road is designed to be able to be expanded in the future, then will likely make it quite easy to do if it’s needed.
Even if four lanes are eventually needed, at least we’d by then we’d have a good understanding of just how accurate the modelling was.
If we have to have Penlink, then building it as a two lane road, at least initially, is the only sensible option