Newshub can reveal that sections of New Zealand's roads are decades overdue for renewal.
The Transport Minister said that's not acceptable and more needs to be done to maintain the network.
The Lyttelton Tunnel is a vital connection between Christchurch and Lyttelton, but the road surface through it is nearly 50 years past its design life – hitting its initial expiry date in 1978.
Nearly a third of NZTA's roading network is overdue for renewal based on what was calculated to be the road's design life. That's the same proportion overdue as in late 2022.
"Clearly it's not acceptable," said Transport Minister Simeon Brown. "Clearly we need to do a better job of maintaining the current state highway network."
The most overdue roads are scattered across New Zealand, including part of State Highway 30 in Waikato with an expiry date of 1996 and part of State Highway 67 on the West Coast expiring in '85.
They're mostly less than a kilometre long, and either bridge decks, which can exceed their design lives as they're non-flexible, or low-volume roads. Renewal plans are in the pipeline for some.
"Those potholes, those road surfacing issues, subsidence, other things that slow transport down... It's the result of the fact there has been a long-term maintenance deficit across successive Governments," said Billy Clemens from Transporting NZ
Road maintenance funding increased under the previous Government, but partially due to the rising cost, the amount of rehabilitation and resealing didn't keep up.
The Government's new draft transport plan increases the funding by $640 million and targets 11 percent of the network being renewed a year.
"We want to see a much more proactive approach, that's why we are ringfencing that revenue, so it can't be siphoned off and used for other purposes," said Brown.
"We are setting those clear criteria and we will be expecting them to be meeting them."
The NZTA said a road's design life is indicative only and based on chip-sealing industry expertise.
It regularly reviews which roads have the greatest need for work, and it's not uncommon for them to exceed their design life and still meet standards.
This is helped by new technologies that mean roads can be maintained for longer than expected.
"Based on the length of the state highway network being approximately 24,500 lane kilometres, NZTA needs to renew approximately 2700 lane kilometres each year to maintain network condition," a spokesperson said.
"During this summer's renewal season, we will have renewed approximately 2,200 lane kilometres by the end of April.
"The volume of renewals we can complete each summer is dependent on a number of factors including funding, contractor capacity and capability, and costs for materials, labour and machinery.
"Over the past 24 months material cost escalation within the construction industry has been well above CPI, which has impacted the volume of work we can complete."
As for the Lyttelton Tunnel, the NZTA said it has a strong pavement with little or no flex in it - and being under cover, it's not subject to harsh weather.
It's penciled in for work over the next year.
