Transport Minister Simeon Brown is crying foul over the amount spent on traffic management, saying it is "eyewatering".

Brown had previously raised concerns over the cost of road cones and temporary speed limits, asking the ministry to look into it.

In a speech at the roading industry's annual Future Roads conference in Hamilton on Wednesday, he shared their findings.

About $786 million was spent on state highway maintenance and capital spending over three years, accounting for 9.3 percent of the government's total transport spend.

"Maintaining our road, water and electrical infrastructure is essential, and some level of TTM (temporary traffic management) is unavoidable. But the current approach is out of control. Excessive use of road cones and temporary speed limit reductions - sometimes left in place when work is complete - simply increases cost, forces people to slow down, and frustrates drivers," he said.

"As a result of the expectations set by the government, NZTA is already responding by implementing a new risk-based approach to how TTM is implemented.

"This new approach shifts away from the blanket use of road cones and temporary speed limit restrictions and towards a risk-based approach which seeks to balance the need to ensure road workers are kept safe, while keeping costs under control."

The minister said initial signs from the first quarter of this financial year were positive, but urged caution on using those figures given they only covered the one quarter during winter months.

"The government will be waiting to see the trend continue to show a reduction in expenditure from what we have seen in previous years, and improved results for roadworkers and motorists."

He said further work would also see local councils reporting their own spending, against benchmarks.

"This figure does not include expenditure by local councils on local roads. Further work is currently underway to provide public reporting and benchmarking of expenditure for local councils in addition to the reporting made by NZTA."

PHOTO: RNZ / Angus Dreaver