Tick, tick, tick…the wait is nearly over for Transmission Gully


The long wait is nearly over for Wellingtonians, with Transmission Gully set to open to traffic within 24 hours following this morning’s ribbon cutting ceremony at the northern end of the newest portion of SH1.

The new road will change the way people move around the region for the better – providing a resilient and reliable route in and out of Wellington, improving safety for everyone, offering better access for communities in eastern Porirua, improving access to the Hutt Valley through a connection with SH58 at Pāuatahanui, significantly reducing traffic volumes on the old coastal route (SH59), and cutting peak travel times in and out of the capital by 7 to 15 minutes in each direction.

“The road has been built to the very highest safety specifications, and we know it will save lives and prevent serious injuries. We’re predicting average daily traffic volumes of 25,000 vehicles per day on the busiest section of the Transmission Gully motorway, between the SH58 and Waitangirua interchanges,” says Waka Kotahi General Manager Transport Services Brett Gliddon.

“It will also remove most heavy vehicle traffic from coastal communities such as Pukerua Bay, Plimmerton and Mana and improve safety and access for people in those areas, as they’ll no longer have the country’s busiest highway cutting through the middle of their communities.”

Waka Kotahi is also reminding drivers that, as with the opening of most major new roads, some disruption and congestion at entry and exit points can be expected as motorists adjust to new road layouts and travel patterns change.  

“It could take a few months for journey times to settle, as people experiment with different routes and become familiar with the new motorway, particularly in the morning for people heading into Porirua and Wellington. We’re asking people to be patient as these new journey patterns settle,” says Mr Gliddon.

There are four new interchanges connecting to communities along the route. Information on how to use them and how local journeys might change is available at www.tg.co.nz.  

Mr Gliddon says people are also advised to avoid the temptation of trying to be the first to enjoy the new motorway.

“We don’t advertise a specific opening time for moving traffic on to any large new road, in order to avoid congestion and the potential for crashes with people queuing up to be first on the new road. We understand why people are excited – Transmission Gully is fantastic, but it will be here for the next 100 years so there is plenty of time to enjoy it. Contractors are hard are hard at work right now completing the final tasks needed to open the road safely.”

The opening of the road to traffic also marks the beginning of the next phase of the Public Private Partnership contract for Transmission Gully, which covers the operation and maintenance of the road for the next 25 years. As the PPP contractor for Transmission Gully, Wellington Gateway Partnership has subcontracted CPB HEB to undertake the motorway’s design and construction, and Ventia to operate and maintain the motorway. After 25 years the road will be handed over to Waka Kotahi at an agreed standard.

Mr Gliddon says even after Transmission Gully opens to traffic, a significant amount of work remains to complete all aspects of the project, and people using the motorway will see work continuing on and around the motorway for some time.

“Over the next 12 months the contractor will be completing parts of the project that were planned for after the opening of the new road. This includes finishing construction of the new section of SH59 between Paekākāriki and Mackays Crossing, completing the project’s walking and cycling tracks and other off-road works, and completing work on the SH58 interchange. There is also more landscaping work to be done once planting season starts again. The southern section of SH59, between Mungavin Avenue and the SH1 Transmission Gully connection at Linden, will also be repaired and resurfaced.”

Transmission Gully - key facts

  • Transmission Gully is one of the largest transport infrastructure projects in New Zealand.
  • 27 kilometres of motorway, with four new interchanges, have been built through geologically and geotechnically challenging and steep terrain with constrained and difficult access, requiring construction of 25 major structures (bridges and large culverts).
  • All structures have been built to withstand a 1 in 2500-year earthquake. The largest structure, Te Ara a Toa, is 230 metres long and 60 metres high.
  • Cuts of up to 70 metres were made through the Wainui Saddle, which also has the Ohariu fault line running through it.  Pouāwhā Wainui Saddle has been lowered to a final crest height of 253 metres above sea level.
  • More than 11 million cubic metres of earth has been moved, the largest volume of earthworks ever undertaken on a roading project in New Zealand. With well over half of the catchment draining into the ecologically significant Porirua harbour, the earthworks required extensive environmental controls including more than 100 sediment retention ponds.
  • The road runs through valleys criss-crossed with streams. As part of the project, around seven kilometres of streams have had to be diverted, and approximately 27 kilometres of streams are being restored, with planting along the banks to provide shade, reduce water temperatures, and improve the natural habitat for stream life.
  • The Transmission Gully project includes one of the largest native planting programmes undertaken in New Zealand as part of a construction contract, with more than 550 hectares of ecological mitigation areas being either retired from grazing or revegetated.
  • The new motorway has been gifted the name Te Aranui o Te Rangihaeata (the great path of Te Rangihaeata) by Ngāti Toa. It references the journey taken by Ngāti Toa Chief Te Rangihaeata after the final stand-off between Te Rangihaeata and Crown forces at Battle Hill, before Te Rangihaeata retreated to Poroutawhao in the Horowhenua.