An indicator of economic activity is showing a dip for August. ANZ Truckometer's heavy traffic index fell 1.5% in August, after jumping 10% in July.
The index measures heavy traffic flows on 11 roads around the country and is an indicator of the current economy.
The light traffic index, measuring flows on 10 selected roads and giving a six month lead on GDP growth, fell 0.3% after rising 0.8% in July.
A senior economist at ANZ, Sharon Zollner, says despite the slight falls, the trend suggests positive economic growth in the September quarter.
"Typically, when you get a series that has large spikes up and down you expect a large increase to be followed by a fall, but in this case it's pretty much held onto its gains, which keeps the upward trends looking pretty good."
She says the trend suggests positive economic growth in the September quarter.
"The heavy traffic index is contemporaneous with GDP so traffic in August is a reflection of economic activity in August - so this is suggesting that Q3 GDP should be fairly good."
Ms Zollner says light traffic predicts the economy six months ahead and that was strengthening six months ago and now truck movements are reflecting that.