Tamati James Rae, 32, was found dead when emergency services arrived at the scene, between Atarau and Ikamatua.
Rae and his children had been visiting family in Hokitika at the weekend and were on their way back to Kaikoura when they crashed on the Atarau Road, north of the Pike River Mine turn-off. The wreckage was spotted by a passing motorist about 8.20pm.
"A passer-by has come across the crash and rescued three children, aged 11, nine and six," senior sergeant Brent Cook, of Greymouth police, said today.
The 17-year-old, a local resident, helped the trio to safety and then got help from a nearby farmer. The children were taken to Grey Base Hospital for observation and were later released into the care of family members, Cook said.
Police were thankful for the actions of the rescuer who had saved the lives of the children, as well as a local farmer who gave them comfort and shelter after the crash.
"This has been an extremely traumatic event for all those involved, and police and Victim Support are continuing to support them, he said.
Atarau farmer Paul Berry, a former Grey district councillor, said the bridge was "beyond its use-by date" and had been the scene of previous crashes, although this was the first fatality he could recall.
It had needed repairing for years and authorities had "unfortunately been dilly dallying around".
"The bridge is no longer fit for purpose and it is essential for the district as the only route for overweight and over-dimension vehicles. It has been a big problem for a number of years now."
In 2012, an elderly man was lucky to survive when his vehicle smashed through the guardrails and fell 5m on to the riverbed. He walked away from crash with minor injuries.
Taylorville man Arthur Foster said his brother also crashed over the side while driving a farm vehicle across it, and he was seriously injured.
"You can't travel on to the bridge at 100km/h. You have to slow right down as there is a sharp bend at the other end," Mr Foster said.
The West Coast Regional Land Transport Plan for 2015-21 ranks the Rough River bridge replacement as a medium rating.
The weekend fatality was the second on a one-lane bridge with wooden guard rails on the West Coast in as many months. In June, a car crashed off the Mai Mai bridge south of Fox Glacier, killing the driver.
West Coast Shuttle owner Cedric Trounson has been campaigning for improvements to those bridges and said today he was saddened to hear they had claimed another life.
The Rough (Otututu) River crash "need never have happened it the bridge had steel armco sides been retrofitted to it".
"Wooden sides are a death trap on single lane bridges, yet still play a low priority with our road improvements. It makes me angry."
He released correspondence with the New Zealand Transport Agency from July, where it said it was assessing the adequacy of the Rough River bridge.
"The problem is twofold - both the width between raised kerb blocks and the wooden handrails should a driver not line the bridge up correctly," NZTA said.
The cost of retrofitting the bridges was very high, it said.
