Build this Brilliant Bridge

This is a guest post by Nicolas Reid, Technical Director – Public Transport and Rapid Transit at MRCagney and author of Transit By Design, outlining a proposal for the next Waitematā Harbour crossing. It is shared by kind permission (via LinkedIn), with some very tasty bonus images.

The proposal in this post strikes us smart, affordable, deliverable, and delightful. A multi-modal bridge, designed to complement the existing one, enabling freedom of movement for all kinds of journeys. A brilliant bridge like this – built beautifully – would be an iconic addition to our great harbour city.

We’re keen for your thoughts. As Patrick highlighted yesterday, Aucklanders deserve a real say on our next harbour crossing. It’s our chance to solve the real problems, and avoid repeating failed patterns. It’s also an opportunity to shape our city for the better, especially given upcoming conversations around the 30-year Integrated Transport Plan! Stay tuned for more on this timely and exciting topic.

Should Auckland build a Waitematā Bridge for its next harbour crossing?

Nicolas Reid 

In this post I present a plan for the Waitematā Harbour Bridge, a multi-modal bridge across the inner harbour east of the existing Auckland Harbour Bridge. A second bridge delivers the huge benefits of an additional crossing aimed at the currrently missing functionality, deliverable at a much-reduced cost and within a much shorter time-frame than previous tunnel proposals.

The Additional Waitematā Harbour Crossing project is in the news again, in the lead-up to officials seeing the latest from twenty-three years of reports and plans for the mega-project. Cabinet will shortly consider a business case, which will undoubtedly present something similar to the designs for extensive motorway tunnels that have been put forward every couple of years since the 2003 report.

Meanwhile the mayor is asking some sensible questions about costs, benefits and time-frames, and presenting some less than sensible alternatives, as various other weird and wonderful schemes are coming to light. So, I thought I would throw my submission from a couple years ago into the ring too.

As a life-long North Shore resident and cross harbour commuter, I’ve experienced first hand a long succession of developments on the harbour corridor through northern motorway widening and through Saint Marys Bay, interchange upgrades on both sides of the harbour, the Victoria Park Tunnel, plus the growth of the first bus shoulder lanes and bus stations followed by stages of busway expansion.

I’ll jump straight in to describe the proposal for now, and follow through with details on the reasoning and analysis in a later article for those that are interested.

The Waitematā Bridge in a nutshell

The proposal is for a new six-lane bridge across the harbour, designed to work in conjunction with the existing harbour bridge to separate motorway and local traffic, while also adding rapid transit and bus lanes, and walking and cycling paths.

It’s aimed at adding the missing modes while also adding missing counter-peak capacity to the state highway. The plan balances the lanes either side of the harbour and separates city commuter traffic from motorway through-traffic, providing resilience and the ability to manage lane closures better.

The Waitematā Bridge alignment. Image: Nicolas Reid/ MRCagney

All up, across the two harbour bridges there would be eight dedicated motorway lanes and two dedicated city traffic lanes, plus a pair of bus lanes from Onewa Road to town. This would match the current twelve lanes that already exist either side of the harbour. It would also add a new separate pair of rapid transit lanes to extend the Northern Busway to the city centre, and walking and cycling lanes to connect the active transport network either side of the harbour.

Unrealised capacity, with twelve traffic and bus lanes either side of the eight-lane existing harbour bridge. Image: Nicolas Reid/ MRCagney

The bridge main works

The main structure is a cable-stabled bridge, 1,800 to 2,000m long itself with 3 to 500m approach viaducts either side. The main deck would be around 38m wide, and would have the same 43m clearance above high tide sea level as the current harbour bridge. However, the approaches would be less steep than the current bridge due to the longer approaches.

A view of the Waitematā Bridge and city skyline from Devonport. Image: Nicolas Reid/ MRCagney

• In the north, it would start from the middle of the motorway at the old toll plaza after the Onewa interchange, bridging straight across the harbour and Westhaven marina to join the Victoria Park viaduct and the Central Motorway Junction just above the Fanshawe Street off-ramps. This alignment directly links the two points where the current transport networks have extra capacity, on the shortest and most direct path.

• A new two-lane extension of the busway would be built on a seaward side embankment from Akoranga to Onewa and the start of the bridge, with a shared path alongside. This would allow the full width of the existing carriageway to be used for ten motorway lanes between Akoranga and the bridges without further widening, and the raised embankment would protect the motorway from storm surge flooding.

• A second on-ramp would be added to Onewa Road for drivers heading south on the motorway, while the existing southbound on-ramp would remain for accessing the city over the existing bridge.

• There would be no works further south than the tie-in to the existing Victoria Park Viaduct and Fanshawe Street. This avoids the need for major tunnelling works and disruption through Wynyard Quarter, Victoria Park and the Central Motorway Junction. North of the bridge landing, all the additional works would be alongside the existing motorway, enabling them to be delivered with lesser impacts.

The motorway and public transport connections on the North Shore. Motorway lanes in blue, city access lanes in orange, bus lanes in green. New embankment with rapid transit and active modes in red. Nicolas Reid/ MRCagney

The Waitematā Bridge and Auckland Harbour Bridge, and connections to existing network at Fanshawe Street and the Victoria Park Viaduct and Tunnel. Nicolas Reid/ MRCagney

Rapid transit, buses and active modes

The new bridge carries a dedicated rapid transit lane in each direction, and walking and cycling paths either side ramping down to Fanshawe Street and the waterfront paths. Bus lanes would run on the outer two lanes of the existing bridge (with traffic exiting to Shelley Beach Road being able to use them as far as the off-ramp), continuing through St Marys Bay as bus-only lanes.

• The rapid transit lanes on the new bridge would initially be an extension of the two-way busway from Akoranga across to the city centre. The geometry of those fully separated lanes would allow them to carry light rail or metro in a future stage, either to the surface in the Fanshawe Street median, or to a viaduct or tunnel extension.

• Buses from the Onewa Road corridor would access the city centre via bus lanes on the existing harbour bridge, much as they do today – while most buses from north of Onewa would use the parallel rapid transit crossing on the new bridge. This separate-corridor design allows bus and rapid transit lanes to be provided but avoids the need for multiple bus access ramps or busway interchanges across the two bridges, although buses from either corridor can still access either bridge using the motorway lanes as needed.

• An Onewa interchange station would allow for interchange between these two corridors, and for local access to Northcote Point. It would have platforms either side of the motorway for the bus lanes, and a busway platform on the seaward side for rapid transit.

Lane balancing and traffic operations

As noted above, the combination of the new and existing bridge would provide ten traffic lanes across the harbour, which balances with the number of lanes that already exist either side. The main improvement for traffic, other than separating commuter and through-traffic, is that it adds the missing counter-peak traffic capacity that is currently removed from the motorway with the variable barrier system.

The network plan for state highway lanes, city traffic, buses and rapid transit across the existing and new harbour bridges. Nicolas Reid/ MRCagney

• The new bridge would have four motorway lanes carrying SH1 southbound to the Victoria Park Viaduct, plus rapid transit, walking and cycling.

• The existing bridge would have four motorway lanes in the centre span carrying SH1 northbound from the Victoria Park tunnel, while the four clip-on lanes would support a local traffic lane and a bus lane in each direction to and from Fanshawe Street and the Pt Erin ramps.

• The movable barrier system would be removed from the Auckland Harbour Bridge, as the two bridges would allow the full peak capacity of five traffic lanes in both directions at the same time. The four lanes of the central span of the existing bridge would all be in the northbound direction, which means they would not need a median barrier. This avoids the awkward single counterflow lane that happens currently, and means the lanes could be wider or have additional separation from the bridge structure.

• For regular operations, the new bridge would match the current Victoria Park viaduct, with one set of two lanes leading to the southern motorway, and the other set of two lanes leading to the Northwestern motorway (SH16), Ports of Auckland, and the Wellesley Street and Cook Street off-ramps. However, the four new bridge lanes could be operate as two lanes in each direction. This allows for resilience for planned closures: in the first instance, the central span and the clip-ons of the existing bridge could be closed in stages for extended renewals and refurbishment, while keeping eight lanes across the harbour as they are today.

Capacity

The dedicated rapid transit lanes, in conjunction with bus lanes and active modes, add a huge amount of capacity across the harbour. Add in the missing counter-peak highway lanes and city access lanes, and the pair of bridges mean an adaptable and robust multi-modal transport spine with massive benefits and resilience.

• The current bridge has capacity for 6,000 (counter-peak) to 9,000 (peak direction) private vehicles per hour each way, plus 7,500 bus passengers per direction.

• The combined bridges would have capacity for 8,000 private vehicles per hour both ways on motorway, and another 3,000 vehicles both ways to and from city centre, plus 7,500 regular bus passengers and another 9,000 passengers per hour each way on rapid transit, plus capacity for up to 5,000 cyclists and 5,000 walkers each way per hour.

Capacity per hour of the current bridge, and the proposed two-bridge system. Image: Nicolas Reid/ MRCagney. (So, 30,000 humans in cars and buses, vs 75,000 humans any way they like)

Other impacts and benefits

• The adjustment of lanes across the old and new bridges would free up three redundant lanes in Saint Marys Bay, unlike some other proposals that would require further widening of the corridor through Saint Marys Bay and into the Marina. This would allow the return of a 15m wide strip of waterfront land to be used for improvements to the beach, public space and Westhaven Drive.

• The bridge would pass over Westhaven Marina, requiring a minor reconfiguration of the berths directly below but allowing 30m clearance over the access channel. The Wynyard Quarter marine industry precinct, superyacht marina and part of Westhaven would remain on the seaward side of both bridges.

• There is the potential to run four lanes northbound through the Victoria Park Tunnel to match the four northbound motorway lanes on the bridge, either by remarking narrower lanes or expanding into the existing width of the main tunnel box with a new emergency escape tunnel (more on that idea to come).

And what about the cost?

To talk about any proposal without a look at the cost is just an exercise in daydreaming. So, to tally up the bill, this proposal is for:

• a 2,000m long six lane cable-stayed bridge,
• 800m of approach viaducts,
• 1,500m motorway widening for an embankment carrying a busway extension,
• an additional on ramp at Onewa, and
• a bus-rapid transit interchange station at Onewa Road.

Comparing to similar bridge projects abroad, the bridge itself should be a $2 to $3 billion proposition. A second harbour bridge is still a huge project, but crossing the Waitematā with a multimodal bridge needs nothing particularly remarkable in terms of bridge design or construction methods.

The connections, embankment and support works should cost no more than half as much again, if we look to things like the SH16 causeway raising project, the Northern Busway extension to Albany, and the motorway works along the Onehunga foreshore. Again, there’s nothing remarkable about the connections either side, and there’s nothing in it that we haven’t already done in Auckland.

This being New Zealand in the late 2020s however, things are more expensive, so we can inflate those figures a bit. But altogether the package should cost less than $6 billion. That seems low compared to many recent project proposals, but it’s important to compare the actual extent and scale of what is, and is not, proposed here.

Most importantly, this proposal avoids a lot of high-cost elements that are part of other harbour crossing suggestions. It is largely an offline construction with minimised impact on the existing motorway or busway. It doesn’t require modifying the Central Motorway Junction, nor does it require major new motorway interchanges built north or south of the harbour. It doesn’t require tunnelling motorways halfway up the north shore, nor extensive new ramps or elevated structures instead.

This proposal aims at getting the best bang for buck by only adding the missing elements, and designing to meet the existing network connections and lane capacity. Designing for a smaller scale project that delivers the main outcomes should lead to a crossing that delivers huge transport benefits, while being affordable enough to actually fund and progress on a realistic timeframe.

So, what do people think? Let me know in the comments!

–Nicolas Reid 

Note: You can click on the images below to see larger versions. For further details of the proposals, see: Waitemata Harbour Crossing Bridge proposal MRCagney (11-10-2024) v3

Across the city

At Westhaven

View from Devonport Wharf

From Maungawhau/ Mt Eden

From Meola Reef/ Te Tokaroa

From the North Shore

Northcote Point perspective

An aerial overview

From St Marys Bay

We like it! And we’ll have more to say in coming weeks. If you’re keen to support Greater Auckland’s work pushing for a brilliant, beautiful bridge as the heart of a top notch 30-year transport plan for our city, you can donate here. And as always, please feel free to share our work widely. This conversation belongs to ALL Aucklanders, and we all deserve to be part of it!

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