A new permanent strut has been successfully installed on the Auckland Harbour Bridge overnight - and southbound lanes will reopen at 9am on Sunday, says Waka Kotahi, the NZ Transport Agency.
"The new strut is now in place, which is great progress and a significant step forward in getting the bridge fully repaired and operational again," said Waka Kotahi General Manager Transport Services Brett Gliddon.
"Our team of engineers now has further work to do to tension the new strut. This key component in this process involves re-distributing the load-bearing capacity of the strut so the bridge's weight distribution is returned to its pre-incident balance.
"This will include constant monitoring to assess how the entire bridge is performing now the new strut is in place."
The southbound clip on lanes that were closed overnight to safely allow the work to be carried out will reopen at 9am. Once the overnight work has been completed, three lanes will be open in each direction.
However the bridge is still not at full capacity. Two lanes on the centre span remain closed.
Waka Kotahi said there would be a further update later today about the timing of the next steps, and the impact this wouldhave on further lane closures in the coming days.
"That means people should continue to use public transport where they can, use the Western Ring Route instead of the Bridge and allow plenty of time for their journeys.
"The Auckland Harbour Bridge is a key strategic asset and it's critical we maintain its long term structural integrity by ensuring there is no lasting damage or new strain put on it.
"We understand how disruptive and inconvenient it is for customers with the bridge operating at 75% capacity and we want to re-open all eight lanes as soon as possible."
The agency said the freak event that led to the damage - a 127km/h wind gust blew a truck over, forcing it into the strut - was unprecedented in the bridge's 61-year history.
The New Zealand-made steel to build the new strut was sourced and fabricated, while teams of engineers worked behind the scenes to model in-depth calculations for redistributing the load-carrying capacity of the bridge once the new strut was in place.
"Waka Kotahi thanks our customers for their patience and understanding while we work as quickly and safely possible to make a permanent repair to the bridge that will open all eight lanes."
The Auckland Harbour Bridge southbound lanes remain closed this morning, as work continues to repair a damaged strut.
The last vehicles allowed to travel southbound across the Harbour Bridge made their way across at 9pm on Saturday. The southbound lanes were due to be closed for around 12 hours.
A motorist on the bridge, which is undergoing repairs after a load-bearing steel strut was badly damaged when a freak gust of wind blew over a truck last month, saw the final vehicles crossing at 9pm.
The two outside northbound lanes remain open and traffic was still moving across at a steady pace, the motorist said.
Earlier, traffic was building heading into Auckland as motorists dashed to get across the bridge before southbound lanes closed at 9pm.
Traffic cameras from Waka Kotahi showed a steady stream of drivers looking beat to the deadline, with all southbound lanes on the bridge closing for around 12 hours.
That's to allow workers to repair the damaged bridge after a shiny new steel strut for a permanent fix to the bridge was transported to Auckland from Whangārei.
The 22.7m strut is in two pieces and travelled on an articulated flat-bed truck on the 160km journey.
The strut has been fabricated from NZ-made steel in Whangārei as a like-for-like replacement and has been painted to match the rest of the bridge superstructure.
On September 18, a freak, 127km/h gust of wind tipped two trucks on their side, severely damaging a load-bearing steel strut causing traffic chaos and bringing the city to a standstill.
A second bout of strong winds barrelling through the Waitematā Harbour at close to 100km/h brought more delays to motorists last Tuesday when authorities temporarily closed the bridge.
A temporary fix was made to the bridge on September 23 when the lower half of the strut was replaced with a section of new steel.
The permanent strut will reach from the bridge overarch to the bridge deck.
There will be reduced capacity on the bridge tonight while work is carried out.
The four centre lanes southbound and northbound will close at 5pm to allow the temporary strut to be removed. At 9pm the two outside southbound lanes will be closed until mid-morning tomorrow, closing all southbound traffic.
The southbound motorway on ramps at Esmonde Rd and Onewa Rd will also close from 8.30pm.
The only lanes to remain open on the bridge through the night are the two outside northbound lanes.
Southbound motorists are advised to use the Western Ring Route on SH16 and SH18 and allow extra time for their journey.
The forecast is for good weather overnight but if the weather is not suitable the closures and the installation will not go ahead and happen on the first available fine night.
Waka Kotahi transport services general manager Brett Gliddon said once the new strut was in place engineers would still need to jack up the bridge deck and connect the new strut as a load-bearing support for the bridge.
"This is by far the most complex part of the process because the bridge needs to be constantly monitored to see how it's responding to the new weight distribution.
"This re-tensioning will need to take place, possibly over several nights, which will involve all southbound lanes over the harbour bridge closing from 9pm to 5am," Gliddon said.
He was confident nothing had been left to chance.
"Checking and re-checking the weight-bearing calculations and then getting our detailed plan peer reviewed by bridge experts overseas. However, there are still many things that all need to go right on the night," Gliddon said.
He said the transport agency was grateful to motorists for the patience and support to work as quickly and safely as possible to make a permanent repair to the bridge that will open all eight lanes.