State Highway Six on the West Coast of the South Island reopened ahead of schedule on Monday, but some claim greater investment in infrastructure could have helped avoid the closure.
Heavy rain last Wednesday caused the Wanganui River near Harihari to break its banks and wash away 40 metres of highway approaching the one-way bridge.
The washout forced travellers from both directions to take lengthy detours.
Sixty seven dairy farmers were cut off from the Westland Milk factory in Hokitika and had to dump up to 450,000 litres of milk.
Westland Milk operations general manager Bernard May said the Transport Agency knew the approach to the bridge was starting to erode before the flooding and more work should have been done to fix it.
But Transport Agency West Coast asset manager Mark Pinner said the bridge and its abutments were up to standard and had been upgraded two years ago.
He said the banks of the river have been strengthened further this time with large boulders.
The 40 metres of restored road has a gravel surface at the moment, but it will be sealed and marked over the next two weeks.