Waka Kotahi recently announced the construction partners for building Ō Mahurangi Penlink, a massive new $830 million, 7 km road through farmland and coastal environment to the Whangaparāoa Peninsula. This comes after the government gave their final approval to the project at the start of the month.
The biggest and most visible change from earlier designs is to the bridge spanning the Weiti River. The reason for the change in design is explained:
“The Penlink alliance will have a strong focus on reducing construction emissions, with a minimum reduction target of 10 percent and a stretch goal of more than 20 percent,” said Mr Kinvig.
“Waka Kotahi identified that the Wēiti River Crossing would be the largest single contributor to Penlink’s embodied emissions, so exploring innovative solutions and ways to reduce its carbon footprint was a strong focus for the alliance during the procurement process.”
During the tendering process the alliance refined the design which now delivers significant improvements from the original bridge, including reducing the number of piers in the Wēiti River, from three to two. This reduces the impact on the marine environment and allows clearer views and passage through the navigation channel.
Construction methodologies have been improved, including a reduction in temporary staging which help to minimise greenhouse gas emissions. A lowered entrance to the crossing will better fit with the landscape, enabling 235 metres to be trimmed off the overall crossing, reducing the amount of steel and concrete required.
A cable supported crossing reduces the amount of concrete required, significantly reducing construction emissions and the northern pier has also been moved away from the coastal cliff to avoid excavation into the cliff face.
For reference, this was the previous design.
They also released a video showing a “flythrough” of the Penlink design:
The road has been designed for a speed of 80km/h but that means it would not be unsurprising to have vehicles travelling at 90 or 100km/h.
A brand new road designed under Vision Zero would not mix active users with vehicles travelling faster than 30 km/hr. So these shared path crossings of the smoothly curved slip lanes is a design that does not qualify as Vision Zero:
A Vision Zero design would include full separation, using overbridges for people walking and cycling anywhere where drivers will be encouraged to drive at speed.
Furthermore, the project provides three interchanges along the route, one to an existing road (Duck Creek Rd) and two for new roads to service planned sprawl developments on both sides of the new highway. Notably, at least some of this development is being planned for by a company chaired by Sir Brian Roche, who is also chair of Waka Kotahi.
Those three interchanges and the bridges that cross the highway should also provide a Vision Zero design for people walking and cycling to allow people to safely connect to/from the Penlink corridor or from one side of the corridor to other. Yet in the flythrough it looks like a miserably proportioned unseparated footpath-making-do-as-a-shared-path:
I guess doing it properly costs a bit more. Which raises the question: At this stage of the “Road to Zero” journey, why is money being spent on Penlink at all, if it can’t be done properly?
While Waka Kotahi appear to be trying to reduce construction emissions, the major emissions culprit will be the vehicles that use the road every day for decades to come.
In December the government released the Climate Impacts for Policy Assessment (CIPA) report for the Penlink project, and there are some serious shortcomings to it. The CIPA summary says,
Changes in enabled emissions arise from use of shorter route with reduced congestion on existing roads.
Yet evidence shows that a shorter route will induce more traffic. Over time, this traffic will grow to the extent that emissions will be higher than without the road.
Penlink is a good example of the “New Link” shown in dashed green lines, in the left scenario, below:
This diagram is from the 2020 California report, Calculating and Forecasting Induced Vehicle Miles of Travel Resulting from Highway Projects: Findings and Recommendations from an Expert Panel, and it says:
Figure 2 illustrates real cases in rural areas where changes in relative accessibility resulting from highway investments led to increased travel—in one case, despite the new route actually shortening the trip between locations.
Assuming the emissions will drop because the extra road capacity will reduce congestion, and because the route is shorter, ignores the shortcomings of the traffic modelling.
The CIPA assessment report shows that the sector’s standard methods for transport modelling were used for estimating emissions for the Penlink project. Below are some pertinent details:
Key assumptions for this analysis include SH1 widening between Albany and Silverdale in the 2048 models, along with a new rapid transit network through Dairy Flat and Silverdale West. Previous analysis on Penlink has shown that wider network effects are sensitive to assumptions on widening of SH1.
I’m sure the assumptions of widening State Highway 1 are very important to how well the model shows the network performs! This is because Penlink will induce traffic on State Highway 1. In the real world, this will lead the people of Dairy Flat and Silverdale West, stuck in extra congestion, to pressure for State Highway 1 to be widened further, which in turn will induce more traffic. It’s how the whole MOAR ROADS cycle of road expansion works.
The government’s Emissions Reductions Plan has now been released, and its requirement to reduce vehicle travel and transport emissions significantly means that widening State Highway 1 can not be considered a given. It’s very cheeky to calculate the emissions for Penlink on the assumption that a future project will “ease” the congestion that Penlink causes on State Highway 1. While there are flaws in all the assumptions involved, the emissions calculations for Penlink should have been done independently of any assumptions about whether State Highway 1 widening will happen.
The CIPA assessment also said:
Induced traffic was included, via the MSM multi-modal model responses. These include mode shift, trip re-distribution and trip re-timing
What this means is that the modelling hasn’t changed. It is still only “reassigning” how people would take their trips, ignoring all the new trips people will take (for a whole lot of reasons). In the framing that Todd Litman of the Victoria Transport Planning Institute gives here, the model used only considered the first and second effects:
Roadway expansion impacts tend to include:
- First order. Reduced congestion delay, increased traffic speeds.
- Second order. Changes in time, route, destination and mode.
- Third order. Land use changes. More dispersed, automobile-oriented development.
- Fourth order. Overall increase in automobile dependency. Degraded walking and cycling conditions (due to wider roads and increased traffic volumes), reduced public transit service (due to reduced demand and associated scale economies, sometimes called the Downs-Thomson paradox), and social stigma associated with alternative modes…
The third and fourth order effects were not included in the Penlink modelling. For example, the CIPA assessment says:
The same land use inputs were used with and without Penlink in place
Yet as the above Weiti development maps show, the land use inputs should have been very different for the scenario involving Penlink, compared to the Do Minimum scenario in which it wasn’t built. There will be much more traffic due to the sprawl the new road enables, all along its length, but the modelling simply doesn’t acknowledge this.
Altogether, these inaccuracies are large and trend in the same direction: the CIPA assessment has significantly underestimated the effect on emissions that Penlink will have.
One thing that may help reduce the impact of induced traffic is if the route is tolled. Waka Kotahi consulted on it earlier this year and we don’t yet know the answer to it. Either way, the final decision on whether to toll the road will be up to the government and so far they’ve rejected tolling on the two roads proposed – Transmission Gully and Puhoi to Warkworth.
And there is already lots of pressure from locals for them not to toll it. Some of those appear to have supported the project being constructed as a toll road right up to the point that construction was confirmed.
The Way Forward
Whangaparāoa streets are themselves in need of a full update. Whether Penlink is built or not, safety improvements are needed throughout the peninsula. And for a fraction of the cost of Penlink, the whole of Whangaparāoa Peninsula could be turned into something children would find accessible, provided through low traffic neighbourhoods and safe paths on the main road. This would lead to enormous bike and bus ridership, providing value-for-money as well as improved wellbeing, modeshift and climate outcomes.
Essentially, there could be lots more of the things that children want:
Like so many parts of Auckland, the unfortunate area has been hit by poor transport decisions multiple times. Penlink comes just a couple of years after the Whangaparāoa Dynamic Lane Project, a project that will induce more traffic along the peninsula. It worsened, rather than improved, safety for people on foot or bike or trying to get to the bus. Here’s the review of the design by Bike Auckland. Even worse, in an earlier business case AT came to the conclusion to build either Penlink or more lanes on Whangaparāoa Rd. It now appears we’re getting both.
So why didn’t Cabinet fund a project of low traffic neighbourhoods and safety upgrades for Whangaparāoa with our tax money, instead?
No one proposed it to them. What Council asked for, was Penlink.
The good news is that Council’s Transport Emissions Reductions Plan (TERP) should be released sometime soon, which will hopefully put Council on a pathway of making responsible requests. With luck, the TERP will clearly lay out why road expansion projects, including Penlink, undermine the transport emissions pathway that Auckland, and indeed New Zealand, needs to follow.
People throughout the city – including children, the elderly, people of different abilities, and those doing all sorts of different activities (not just commuting) – will be far better served if we weren’t wasting our taxes on highways and road expansion, but were concentrating on improving places, safety and accessibility. We can choose to provide healthier, lower-carbon, lower maintenance transport systems so our children face lower public health, carbon credit and maintenance costs. Given the economically and ecologically uncertain future they face, it seems like the least we could do for them.