How Transmission Gully would have made a difference

The Dom Post reports:

The Transmission Gully motorway could have provided a lifeline to almost 23,000 motorists stuck in gridlock during Wellington’s flooding.

Traffic modelling by the New Zealand Transport Agency suggests the planned inland motorway between Porirua and Paekakariki – scheduled to open in 2020 – would have significantly altered the civil defence emergency experienced across the region on Thursday.

With State Highway 1 closed by a landslip on the coast road between Pukerua Bay and Paekakariki, and SH2 at Petone submerged by floodwaters, about 30,000 people found themselves stranded in the capital. …

Even without natural disasters, Transmission Gully is expected to make a massive difference to traffic flows, reducing the number of vehicles using the coastal SH1 route to just 3090 – a drop of 86 per cent.

Raewyn Bleakley, the transport agency’s central region director, said the contract for the motorway, which is being built by a private consortium, sets out high standards for resilience to earthquakes, landslips and crashes.

The four-lane Gully route would be far more likely to stay open during a landslip than the existing two-lane coastal highway, which showed its vulnerability on Thursday, she said.

And we’re actually going to get it this decade, after 70 years of waiting.

Bruce Pepperell, civil defence controller for the Wellington region, said comments on the Civil Defence Facebook page during the flooding suggested Transmission Gully had never been so popular.

“It can’t come quick enough,” he said.

“When you’ve only got two main roads out of town, and they’re both gone, then you’re not playing with many aces up your sleeve.”

The pace with which SH1 and SH2 north of Wellington were both knocked out had civil defence staff “sweating” about the prospect of trying to find space in Wellington for an extra 30,000 people overnight, he said.

A Civil Defence-led report in 2013 predicted the Gully motorway would be of even greater value after a major earthquake of magnitude 7.5 or more, which is expected to severely damage Wellington’s main transport links.

Which is why I support it – it is not just about congestion. It is about Wellington not being cut off.