Option A bridge to free up NZ's busiest roundabout


The NZ Transport Agency has announced its plans to progress the 'Option A' bridge option around the Basin Reserve to untangle traffic congestion and free up space for public transport, pedestrians, and cyclists.

NZTA Wellington state highways manager Rod James says the NZTA has made its decision as part of apackage of proposed improvements to State Highway 1 between the Mt Victoria and Terrace Tunnels, which also includes improvements to the existing Inner City Bypass. The improvements will free up bottlenecks, shorten travel times and reduce the impact of SH1 on local traffic and public transport throughout the Eastern CBD.

Mr James says the decision to progress Option A comes after extensive analysis of public feedback, and will include a dedicated pedestrian and cycle lane. The bridge is designed to benefit public transport users, pedestrians, cyclists, motorists and airport freight by helping to free up the Basin from the heavy demands of highway traffic.

Mr James says the NZTA has investigated calls to put the state highway into a tunnel that extends to the Mount Victoria Tunnel, but extensive studies had shown this would be impractical, disruptive and expensive due to the swampy ground conditions and difficult topography.

“We need to fix the problem of opposing streams of traffic competing for limited road space around the Basin.

“The Basin Reserve is the country’s biggest and busiest signalised roundabout.  We need to untangle the mess around the Basin, and doing nothing is not an option. Squeezing large volumes of state highway traffic through this constrained road layout is clogging up the whole system, causing delays to buses and traffic heading between the CBD, the Eastern and Southern suburbs and the Airport.”

He says a bridge will not only make travel easier for those using the bridge, but also for those travelling below it. The result will be a balanced transport solution that works for all travellers, with time, petrol and money saved for motorists and public transport, and safer, dedicated facilities and an improved Basin precinct for pedestrians and cyclists.

“The bridge will lift state highway traffic out of the way of buses and other local traffic.  This gives the Basin precinct more breathing space to allow wider footpaths, a pedestrian plaza outside the Basin front gates, better school drop-off facilities for buses and parents, and improved safety for school students and cricket fans due to the improved pedestrian facilities and fewer cars to negotiate.”

Mr James says the improvements at the Basin Reserve and Inner City Bypass will also deliver some of the key benefits sought in the Ngauranga to Airport Corridor Plan – a plan that is endorsed by the NZTA, Greater Wellington Regional Council and Wellington City Council, and other members of Wellington’s Regional Transport Committee. A pivotal part of this plan is the separation of competing streams of traffic at the Basin Reserve, allowing public transport to flow more freely through this area and helping to free up a future dedicated corridor for buses or light rail. Achieving this separation is critical in unlocking the possibilities of the Public Transport Spine study which is currently underway.

Mr James says the improvements would also help to reduce the number of motorists avoiding the Basin Reserve bottleneck by using local roads such as Oriental Bay that were never intended as high-volume commuter arterials. Traffic volumes around the scenic Oriental /Evans Bay Parade route are projected to increase significantly if nothing is done.

Mr James says the decision to progress Option A, the bridge 20 metres north of the Basin Reserve’s northern entrance, was made after careful consideration of public feedback.

“Public feedback showed a clear preference for a pedestrian and cycleway to be attached to the bridge, so we’ve listened to this feedback and built it into our plans. This means pedestrians and cyclists travelling between Paterson and Tory Streets will be able to go straight across without negotiating the roads around the Basin Reserve.”

“We also received feedback that Buckle Street should be put underground.  The Government has provided additional funding to enable the new Memorial Park underpass, and our plans for a bridge always allowed for the prospect of Buckle Street being undergrounded.

Mr James says the NZTA recognises that the decision to build Option A won’t please everyone.

“We know that there are some concerns about the effects of a bridge, and urban design will be absolutely paramount as we progress design. A big part of our job will be working with affected parties, urban designers, the Historic Places Trust and the councils to ensure that we design this project to respect the heritage and sensitivity of the surrounding environment.”

 Mr James says Option A was preferred to Option B largely due to its more direct route and fewer property impacts. The NZTA also extensively investigated tunnelling, but this was not practical.

 “It would be difficult to think of a more problematic place on land to build a tunnel. Our geotechnical investigations have shown that, due to the very high water table, the ground directly under the existing road is sludgy, and it would be like building a tunnel through a swamp. Due to the hilly topography, such a tunnel would also have to be V or U-shaped and would be very steep. Construction of a tunnel would have a huge impact on traffic due to the lack of space for a temporary road, and it would also have high ongoing operating and energy costs due to the need for 24/7 lighting, monitoring and ventilation.

“Tunnels also have a surprisingly large visual impact.  A tunnel in this vicinity would likely require a large portal around the side of the Basin, a pumping station near the front gates, and ventilation stacks in the vicinity of Memorial Park.”

Mr James says the bridge will be built to withstand a one in 2500 year earthquake, whereas a tunnel in a swampy underground environment would be much more seismically vulnerable and more prone to liquefaction.

He says the NZTA has also looked at the Architecture Centre’s Option X proposal, but it was not considered workable as it would require significant property acquisition, a three and a half storey climb for pedestrians and cyclists, numerous pedestrian and general traffic problems, and a large design footprint that undermined the desired efficiency and safety gains.

He says the NZTA also investigated ‘ground level’ options, but these did not work effectively as an enduring solution as they did not provide the road space necessary to efficiently accommodate both public transport and a large number of vehicles.

Mr James says the NZTA are starting to finalise its design for the bridge, and would work closely over the next few months with councils, affected parties, the Historic Places Trust, and urban design experts to refine the designs, design and take on board further feedback

The NZTA is also aware of concerns about the impact of the bridge on the Basin Reserve ground. The Agency will be working specifically with the Wellington City Council, Basin Reserve Trust and the Historic Places Trust to pursue a stand as a mitigation measure, contingent on it achieving the necessary consents, and the support of those parties. 

Mr James says that once the designs were finalised, the public will have the opportunity to give formal feedback through the Resource Management Act process, which is expected to commence in early 2013.

He says the NZTA will also be improving intersections along the existing Inner City Bypass to make the road layout work better for everyone.

“We’ll be tackling the intersections that aren’t running as efficiently as they could be, by improving the layout and the signal phasing. Giving these intersections a makeover will improve their operation for all transport users, whether that’s cross-town traffic or motorists, cyclists and buses heading between Brooklyn and the CBD.”

The Tunnel to Tunnel improvements, including the undergrounding of Buckle Street, are part of the Wellington Northern Corridor Road of National Significance, which will improve economic productivity, ease congestion and improve safety throughout the Wellington region.

The ‘Option A’ bridge runs from Paterson St to Buckle St, and is located 20m north of the Basin Reserve. Both Option A and Option B - which would run 65 metres north of the Basin Reserve - were put forward for public feedback in mid 2011 as part of a package of proposed improvements between Cobham Drive and Buckle Street. Construction on the bridge is expected to begin in mid to late 2014 and be completed by mid to late 2016.

Full details will be online from 10am at www.nzta.govt.nz(external link).

Why Option A?

  • Separation of north-south and east-west traffic was agreed upon in the Ngauranga to Airport Corridor Plan, co partnered by NZTA, GW and WCC and consulted upon with the wider Wellington community. The NZTA has determined that grade separation is pivotal to achieving this separation and relieving congestion here, because we need to physically separate the traffic in order to release pressure on capacity
  • A bridge works best of all options considered in terms of relieving congestion and improving travel for all forms of transport
  • As well as being the most effective option, it is also cost effective
  • It takes the country’s most clogged roundabouts out of the equation for around 25,000 vehicles per day and saving time, petrol and money between the Eastern Suburbs and Buckle St
  • It separates state highway traffic, meaning less traffic around the Basin Reserve at ground level and less conflict between opposing traffic streams
  • It will make public transport journeys quicker by lifting heavy volumes of state highway traffic out of the public transport spine
  • It frees up potential road space for a future dedicated public transport solution
  • It provides a dedicated pedestrian and cycleway that is expected to encourage more walking and cycling in the immediate area
  • It’s safer for pedestrians; fewer cars for pedestrians such as school children and cricket fans to negotiate, and wider footpaths and an new pedestrian plaza for students and cricket fans to spill out onto, and enables better school drop-off facilities for buses and parents
  • It will mean fewer cars travelling around Oriental Bay and through Newtown trying to avoid the Basin Reserve congestion.
  • It’s more earthquake resilient than a tunnel, with lower running costs and operating emissions than a tunnel
  • While the NZTA recognises some concern about the visual and noise effects of a bridge, the NZTA is committed to working with urban design experts, councils and affected parties to address these
  • It requires fewer properties than Option B.

Why not a tunnel?

  • Prior to seeking public feedback on Option A and Option B, the NZTA had already extensively investigated tunnel options (as well as surface options)
  • The Basin Reserve used to be a lagoon, and geotechnical investigations over the last year have shown that the ground is swampier than previously thought
  • A bridge is far less vulnerable to an earthquake than an underground tunnel located in swampy soil
  • A tunnel would need to be built deep, creating a vertically V or U shaped route with potentially sharp gradients
  • A tunnel would cause major traffic chaos during construction for years, as there is no room for a temporary road
  • Tunnels need to be lit and ventilated 24/7. This uses more energy, costing more and resulting in higher emissions
  • A tunnel would likely need ventilation stacks at Memorial Park and a large pumping station by the Basin Reserve
  • A tunnel portal would cause significant visual impacts and severance around the Basin Reserve
  • A tunnel would be very steep – an 8% gradient is not considered to be desirable from a safety perspective – it would be like travelling down the Nguaranga Gorge, but in a tunnel.