A spokesman for Waka Kotahi said that the stretch of road on which the Picton crash occurred was not slated to have a median barrier installed, as prior to Sunday's crash there had been one fatality and no serious injuries recorded there since 2012.
By contrast, Waka Kotahi has installed a median barrier along a 3.5km stretch of Centennial Highway north of Wellington where there have been 17 fatalities and 15 serious injuries.
The rollout of median barriers was funded as a result of directions issued in the 2018 Government Policy Statement (GPS) on land transport, which shifted funding towards road safety.
The GPS tells Waka Kotahi what priorities the Government would like to see in transport spending. The 2018 GPS resulted in Waka Kotahi setting aside $3.6b for safety-related benefits in the 2018-21 National Land Transport Plan or NLTP. The 2021-24 NLTP invests $2.9b in safety.
Green Party Transport spokeswoman Julie Anne Genter, who was an associate transport minister when the 2018 GPS was written, said the Government could and should roll out more median barriers.
Genter reckons the Government could install about 2250km of median barriers if it spent all of the $3.6b allocated to safety on installing them.
That would be enough to install barriers down the entire 2033km of State Highway 1 (some of SH1 already has median barriers).
"You wouldn't spend it all on median barriers necessarily, but it shows you comparably how little they are putting in relative to a budget that they say is about safety," Genter said.
Genter thought her costings of median barriers were conservative.
"Even if that [the cost] doubled, it would still be well over 1000km," Genter said.
Genter said countries like Sweden, Norway had taken a "vision zero" approach to safety, which had included more median barriers.
"Part of that had included cost-effective upgrades like median barriers and passing lanes and side barriers, where appropriate, over large areas of their more rural network," Genter said.
"Ireland and Norway stand out as countries that are quite similar to New Zealand in terms of topography and rural highways."
She said that Waka Kotahi, under the former National government, pivoted its focus to motorways in urban areas at the expense of improvements to rural roads.
Transport Minister Michael Wood said the "deployment of median barriers is a key part of the Road to Zero programme, which I expect Waka Kotahi to give appropriate priority and energy to".
The Road to Zero programme is a Government strategy that hopes to reduce road deaths to an aspirational target of zero in the long term.
He said he would continue "to monitor their progress and expect the pace of the barrier roll-out to increase over the coming year".
National's transport spokesman Simeon Brown said the sluggish rollout of median barriers was a failure of delivery.
"This is just another example where the Government has promised big on road safety but absolutely failed to deliver," Brown said.
"We see the Road to Zero policy being rolled out but it's not being delivered other than TV advertising," he said.
Brown said Wood lacked a focus on "outcomes" and "leadership".
Brown acknowledged the tension between funding safety improvements to existing roads and building new roads.
"I think road safety is important, but building new roads is also incredibly important, because those roads have incredibly good safety ratings," he said.
"We've got a Government that is devoting an incredible amount of money to road safety, but New Zealanders aren't seeing the results of that spending."
As associate transport minister in the Government's last term, Genter fought a political battle with National over the merits of funding safety improvements on existing roads at the expense of building highly specced new roads, known as Roads of National Significance or RoNS.
Many RoNS were cancelled as a result of the funding directions made in the 2018 GPS, which shifted funding to safety and maintenance.
Genter stood by this shift in focus.
"Even if you went on the best timeframe of the RoNS, they haven't completely finished what [then Transport Minister] Steven Joyce announced in 2009, that will only improve the network for 4 per cent of daily vehicle trips," she said.
"90 per cent of deaths and serious injuries would not be prevented by the programme.
"We want to be covering a wide part of the network, because the places were people are dying and getting seriously injured are really spread out."
A Waka Kotahi spokesman said installing the barriers was time consuming than often appeared.
"Median barriers are very effective, but they are also time consuming and relatively expensive to install. We are looking at ways of delivering them more quickly, but there is often other work which needs to be undertaken as part of the installation - that includes widening roads, moving utilities (power, gas etc…), and work like intersection improvements and providing safe turning facilities to allow people to access properties," he said.
"When all of these costs are included, the total cost of installing median barriers is between $2.5 million and $3 million per kilometre. [The cost of the material only ranges from $75,000 to $150,000 per kilometre]. So while they are effective and relatively inexpensive, they are not a 'cheap' or easy fix."