ANZ's Truckometer indicator is pointing to an economy with a lot of momentum.
The heavy traffic index eased 0.9 per cent last month, but the September quarter as a whole has recorded the strongest quarterly increase in its 13-year history.
"It suggests a potentially spectacular September quarter GDP result," said ANZ economist Sharon Zollner.
The heavy traffic index tracks trucks on 11 roads that have historically matched the economic output at the time.
The index has shown a steep upwards trend in the past six months. The Truckometer, released yesterday, also has a light traffic index, which tracks cars and vans, and which provides a pointer to activity six months ahead.