Motorcycle crashes and drivers plunging down the steep banks of the Rimutaka Hill Rd have contributed to it being named one of the riskiest in the country.
A KiwiRAP report for 2012 shows State Highway 2 from Featherston to Upper Hutt is the riskiest road in Taranaki, Manawatu, Wanganui and Wellington regions.
The next highest risk was on State Highway 1 from Paraparaumu to Levin.
The New Zealand Transport Agency has spent $16.5 million on realigning 1km of road on the hill near Muldoon's Corner, which was completed this year.
On the Rimutaka Hill route, there were two fatal crashes and 32 serious injury crashes between 2007 and 2011.
Last month, an Upper Hutt woman crashed off a steep bank and was found in thick bush 100m below, having suffered minor injuries.
Featherston Fire Brigade chief Colin McKenna said accidents he recalled included motorcyclists being hit by buses and cars, and vehicles going off the side of the hill.
"We've been to some pretty good crashes up there - several where people have gone over the side."
From his experience, wet roads and speed were factors in many crashes. He said crashes had occurred travelling to and from Wairarapa.
Mr McKenna expected the road improvements would make the road safer to drive.
McCarthy Transport manager Stan Sayer, who has been in the trucking business for about 40 years, said local drivers negotiated the hill easily.
"Basically, they're so used to it," he said."
"Everybody knows what it's like and it's part of our job, really."
But Mr Sayer said truck drivers from out of the region, who may not drive the hill as often, would find it difficult.
"They're the ones that would have trouble with it."
He had seen many alterations to the road over the years but was particularly happy with the most recent.
"The last improvements were the best ones that have ever been made."
Statistics for 2007 to 2011
State Highway 2 from Featherston to Masterton
Serious injuries: 10
Fatal Crashes: 2
Risk Level: Medium-High
State Highway 2 from Woodville to Masterton
Serious injuries: 22
Fatal Crashes: 7
Risk Level: Medium
State Highway 53 from Featherston to Martinborough
Serious injuries: 2
Fatal Crashes: 0
Risk Level: Low