Auckland’s missing motorway has been hiding in plain sight for seventy years
- Grant McLachlan
- 6 days ago
- 4 min read
The Eastern Motorway — State Highway 17 — has a vacant number, protected land, and a proven funding model. All it lacks is a government with the wit to act.
Something nobody in this city seems willing to say out loud: We built a motorway on the wrong side of Auckland.
The Western Ring Route — SH16 across the Northwestern Motorway, through the Waterview Tunnel, and down SH20 to Manukau — is a genuine engineering achievement. When the Waterview Tunnel opened in 2017, it immediately diverted seven percent of traffic off SH1. That reduced daily congestion across the Auckland motorway network by the equivalent of 10,000 hours. Every day.
The eastern side of Auckland has nothing. Not a metre of dedicated motorway. Over 300,000 people in Howick, Pakuranga, Botany, Flat Bush, Manukau, Mt Wellington, Panmure, Glen Innes, and the eastern bays all funnel through arterial roads to the same pinch point: State Highway 1, the most congested road in New Zealand.
Consider what that means. State Highway 1 runs directly through the middle of the country’s largest city, with almost no alternative routes for local traffic. If something goes wrong — a crash, a high-wind event, a structural failure — the North Shore is effectively cut off from the south. This is not a hypothetical. The Auckland Harbour Bridge has been closed twenty times since 2020, accumulating over $35 million in documented economic damage.
One bridge. One motorway corridor. 1.6 million people. In what world is that acceptable transport planning?
The answer has been sitting on a map since the 1950s. It is called the Eastern Motorway. Its proper designation would be State Highway 17.
SH17 is not a new idea — it is a vacant number. NZTA revoked the old SH17 designation in 2012 when the Hibiscus Coast Highway was downgraded to an urban route. The number has sat unused for over thirteen years. Under New Zealand’s numbering convention, SH10 through SH19 belong to the Auckland and Northland regions. SH16 is the Northwestern Motorway. SH18 is the Upper Harbour Highway. SH17 belongs on the eastern corridor. It always did.
The route itself is largely protected — and much of the land is already vacant or publicly owned. The Onehunga industrial waterfront. The rail corridor from Sylvia Park through Panmure. Stanley Bay Park and Bayswater Park on the North Shore. The Hillcrest Creek Reserve. The Eastern Transport Corridor designation has been on the books since the 1950s, surviving every government, every planning fashion, and every round of motorway cancellations. Nature and decades of planning have done much of the preparation. Nobody has had the wit to follow through.
The route runs 22 to 25 kilometres from SH20 at Onehunga Harbour Road, along the harbour edge to Sylvia Park, up the rail corridor through Panmure, across Hobson Bay by tunnel, interchanging with the inner city at Tamaki Drive, then under the Waitematā Harbour to emerge near Bayswater and connect into SH1 north of Esmonde Road. Six lanes — three each way — to the same standard as the Waterview Tunnel.
The demand numbers are not speculative. Apply the Waterview precedent to the eastern catchment — larger population, zero existing motorway access — and the Eastern Motorway carries around 80,000 vehicles a day at full operation. Applied to the SH1 corridor between Sylvia Park and Northcote, which currently carries 100,000 to 155,000 vehicles a day at or above capacity during peaks, a conservative diversion of ten percent removes up to 15,000 vehicles a day from the worst pinch point in the country.
The economic benefit runs to approximately $1.56 billion a year in travel time savings, crash reductions, and freight productivity gains. Over a forty-year project life, the net present value of those benefits is around $22 billion. The maximum construction cost at which the project still delivers a positive return is also around $22 billion. The engineering estimate for a fully tunnelled route with two major water crossings is $12 to $18 billion. The numbers work.
Now the funding. The Auckland Harbour Bridge carries 155,000 vehicles a day — free. Sydney tolled its harbour bridge for decades. Those revenues funded the Lane Cove Tunnel, the Cross City Tunnel, and eventually the Sydney Harbour Tunnel itself. Toll the Auckland Harbour Bridge at $5 to $10 per crossing and you generate $280 to $560 million a year. Over a thirty-year concession, that is $8 to $17 billion — enough to finance the bulk of the Eastern Motorway, including its new harbour crossing.
We would be tolling a bridge to build the alternative that takes pressure off it. The Sydney model, applied to Auckland.
The Eastern Motorway. State Highway 17. The route corridor is designated. Much of the land is there. The demand is proven by precedent. The funding mechanism exists. All it takes is a Gazette notice to assign the number — the smallest possible act of political courage, and the most important first step.
Someone in Wellington should do that. It would take about ten minutes.
Attachment
The feasibility analysis summarised in this column is set out in full in the attached Indicative Business Case for the Auckland Eastern Motorway (State Highway 17), prepared in accordance with NZTA’s own Business Case Approach and Monetised Benefits and Costs Manual. The modelling uses NZTA’s published methodology and the best available traffic volume data. It is, however, constrained by the same limitation that undermines every Auckland transport study: neither NZTA nor Auckland Transport has deployed licence plate recognition technology to establish where traffic on SH1 actually comes from and where it goes. Until that origin-destination data exists, all demand modelling — including this business case — relies on volume counts and precedent rather than direct measurement. The case for the Eastern Motorway is strong enough to survive that uncertainty. The case for collecting the data properly is, if anything, stronger still.
