The Government is being taken to task for increasing truck sizes from 44 to 50 tonnes but not boosting funding so roads can cope with the extra weight.
"Local councils are building bridges to their 44-tonne funding, so the new and bigger trucks will be unable to use the roads," said New Zealand Groundspread Fertiliser Association president Stuart Barwood.
Whangarei District Council (WDC) roading manager Jeff Devine confirmed the NZ Transport Agency (NZTA) was proposing to allow trucks to carry 50 tonnes, rather than the 44 tonnes now approved.
"But this is only to be done with council approval on council roads," he said. "Council would need to check the road and issue a permit to allow it to be used for 50-tonne trucks."
The 50-tonne trucks - called 50Max - had an extra axle to spread the load, so impact on the road pavements was minimised. However, they could have some impact on particularly long bridges because of the extra total weight.
Mr Devine said the WDC had requested NZTA funding this year to upgrade two bridges on Mangakahia Rd, to enable them to carry 50Max trucks.
The impact of 50Max on other roads in the district was now being investigated.
"It is intended that roads and bridges not capable of carrying 50Max loadings would be signposted to warn 50Max drivers not to use these roads, similar to our current system of weight restricted bridges that are not capable of carrying the standard 44T loads," Mr Devine said.
WDC has also requested additional NZTA funding of $1.3 million annually for maintenance and renewals.