Truck and tractor drivers taking shortcuts are being blamed for causing hundreds of thousands of dollars of damage to Taranaki landmarks.
The New Plymouth District Council says the historic Uruti Tunnel and Bertrand Road Bridge are being smashed up by drivers forcing oversized vehicles through them.
The Bertrand Road Bridge was built in 1897 and reconstructed in 1927.
Only ever designed for cars, larger vehicles are forcing their way through bollards at each end of the 125-year-old bridge, destroying wooden railing and its decking.
The 235-metre Uruti Tunnel was built in the 1920s and its support timbers and girders are now being bent out of shape by oversized vehicles.
NPDC transport manager Rui Leitao said it was costing ratepayers about $150,000 a year to make repairs to similar structures across the district.
"This sort of damage makes these roads dangerous for other drivers and costs ratepayers hundreds of thousands of dollars to fix. We've spent $60,000 alone fixing the Urutī Tunnel over the last two years. The repair work also holds up other traffic. And the really frustrating thing is that it's all totally avoidable."
Leitao said the council was working with trucking companies to solve the problem.
"We're steering drivers to use navigation apps designed especially to take big vehicles over suitable roads, because too often we see them relying on standard GPS or just chancing a shortcut.
"We suspect some drivers have even climbed on top of their cabins to move height restriction signs at tunnel entrances and in 2014 a big truck actually got stuck in the Urutī Tunnel."
Leitao said the council attempted to recover the costs of damage to its structures, but too often the culprits were gone before the damage was reported or found by maintenance crews.
All the council's tunnels and bridges had signs ahead of them warning of size and weight limits, so there was no excuse for using them, he said.
Fast facts
NPDC maintains more than 1300km of roads, including 272 bridges and five tunnels.
This includes 963km of rural roads of which 169km is unsealed.
The council spends about $7.5 million each year on road maintenance (about $3m on the rural network and $4.5m on the urban).
About 80 percent of this expenditure attracts a 51 percent subsidy from Waka Kotahi.
Total spend on roads across the district is about $20m annually.
This figure includes $6m on the rural road network with about $1m going on unsealed roads.
Vehicles travel about 262 million kilometres on New Plymouth's roads each year.
RNZ