Auckland Harbour Bridge: Why is NZTA closing lanes in high winds?
Tuesday, 29 September 2020
Tuesday morning saw the Auckland Harbour Bridge close completely to motorists for about an hour as wind gusts reached 98 kilometres per hour.
Waka Kotahi NZ Transport Agency has warned that further lane closures are possible if severe gusts continue.
It comes after the bridge was severely damaged on September 18 when a “freak’ gust of wind blew a truck into the bridge.
A temporary fix to the bridge means three lanes are currently available in each direction. A permanent fix is likely to be installed on Saturday night.
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**
Why is the bridge being closed when there are high winds?
Waka Kotahi NZ Transport Agency said the answer to this is “reasonably straightforward”. It can’t risk the possibility of wind causing another truck to blow into the already damaged bridge again.
A spokesman for the agency said ongoing wind gusts have been a concern since the weekend and its bridge team is continually measuring wind levels.
“It is vital we protect this critical piece of infrastructure for the medium and long term.
“If another incident were to occur because of high winds the bridge could be damaged even more which would cause longer term disruption.”
The spokesman said safety is top priority and it will not take any chances due to the “superstructure’s” current damage.
How gusty does it have to be for lanes to be closed on the bridge?
The transport agency earlier said it would have to close the bridge if wind gusts exceeded 80kmh.
It said the closures could happen at very short notice and it acknowledged the disruptions this could cause – but safety was more important.
On Tuesday morning, the bridge was closed around 7am because of severe gusts.
“A squally cold front crossed over the Auckland Harbour Bridge just before 7am, with peak gusts of 98 kmh observed,” the agency said.
It was reopened around 8am.
What wind direction affects the Auckland Harbour Bridge the most?
MetService meteorologist Georgina Griffiths said cross winds are usually the worst.
“That’s a westerly or a northwesterly is probably even worse. The gust to 98kmh this morning was a cold front just before 7am and was a west to northwesterly gust.”
How often does Auckland experience high winds?
MetService meteorologist Sonja Farmer said Auckland gets its highest winds around this time of year.
In August 2019, strong winds saw the roof of The Cloud events centre on Auckland’s Queens Wharf lifted.
In April 2018, a storm saw wind gusts reach hurricane force overnight on April 10-11. Gusts reached 100-150kmh across central Auckland. Gust peaked at 213kmh at Manukau Heads.
A storm in January 2018 saw strong winds rip boats of their moorings and then smashed into rocks in Algies Bay.
What caused the damage to the harbour bridge in the first place?
Around 11am on September 18, strong and sudden gusts toppled two trucks as they crossed the bridge, Brett Gliddon, NZTA transport services general manager, said.
One was at the peak of the bridge when it was knocked over by a gust and slammed into a steel beam, twisting the metal and shearing it clean off where it connected to the bridge below the road surface.
Gliddon said the wind was an acceptable 60kmh before it shot up to a gust of 127kmh before dying down again.
“We were hit by an absolute freak gust of wind which caught a truck as it was right on the top of the bridge. That's really hard to design for.”