Ask Phoebe: No third lane for Mt Wellington bridge

An aerial view of the Mt Wellington interchange of Auckland's Southern Motorway, looking south. Photo / Dean Purcell

The building of bridges and tunnels at the Waterview interchange is proceeding at a steady pace, but I've noticed one part of the construction that is being treated differently.

For weeks now one particular bridge joint has been shrouded in scaffolding and hidden behind plastic sheeting. I don't recall any other part of the construction receiving so much attention.

Is there something wrong with this bridge joint? Why is it hidden from view?
- Warren Hurley, Auckland.

A batch of concrete delivered to the project did not meet the Waterview Connection's quality standards and was removed from a section of the Great North Rd Interchange. High pressure water blasting was used to remove the concrete.

The work area was screened for safety and environmental reasons, to protect people and traffic using both the motorway and cycleway below, during water blasting. It also acted as a buffer to reduce noise levels for people living near the interchange. The concrete has been removed successfully and is being replaced.

Is there any plan in the pipeline to widen the motorway at Greville Rd? The extra lane northbound from Constellation was a great success.
- Estelle Seaman, North Shore.

The Northern Corridor Improvements project will widen the Northern Motorway to four lanes in each direction from Oteha Valley Rd to Constellation. This includes past Greville Rd southbound. Construction on this project is due to start in 2018.

The project team is currently working through planning and resource consents. The project also includes an extension of the Northern Busway from Constellation to Albany, improving travel choices in the area, and a new direct motorway connection to Upper Harbour Highway (SH18), providing the northern-most link in the Western Ring Route.

I use the Southern Motorway every day and like most people, have noticed the density of traffic progressively getting worse. As my car crawls over the two-lane bridge at Mt Wellington each day, it's hard not to notice that it was constructed in 1955.

The Mt Wellington bridges are just two of the bottlenecks on the motorway system. Is there any plan in the near future to build an extra lane?
-Rob Mackley, Auckland, Karyn Sanson, and myriad others.

No. Last year the Transport Agency considered options for widening the Southern Motorway at Mt Wellington. Investigations showed that an additional lane here would have the effect of increasing congestion at the Southeastern Arterial and Ellerslie-Panmure interchanges which would negate any benefits achieved by an additional lane. Because of this the Transport Agency has no current plans to widen the Southern Motorway at this location.

However, the long-term answer to some of these congestion points is better utilisation of the entire network. One of the key benefits of the Western Ring Route when it is completed is that it will provide effective alternative options to the southern corridor, easing pressure on areas such as the Mt Wellington interchange.