The project, which will cost $29m over the next three years, include safety upgrades between Raleigh St and Waiongana Stream.
Twyford said this was a "state-of-the-art" safety upgrade.
"New Plymouth has had a pretty steady population increase, and along this corridor there had been quite a lot of land use change – people building homes and businesses out along the highway."
This means traffic volumes are relatively high for the area, meaning it has been "particularly dangerous".
Twyford said a new right-turn pocket on SH3 into Wills Rd will be built, with an extension of the right-turn pocket into Corbett Rd following.
There will also be SH3 widening between Wills/Corbett and Mahoetahi Rd for wide shoulders with wire rope safety barriers.
"State Highway 3 is one of the busiest stretches of road in the region, carrying a mix of freight and commuter traffic, and provides access to New Plymouth Airport and the Port," Twyford said.
The improvements would also include several new roundabouts at key intersections.
Twyford added that NZ Transport Agency is prioritising urgent safety improvements to make them more forgiving of human error.
"Drivers will always make mistakes and the Government's job is to stop those mistakes turning into tragedies."
He said the community had been asking for safety improvements to be made on the road for "some time".
In fact, New Plymouth's Mayor, Neil Holdom, had been a "very strong advocate" for the improvements.
The Government is investing $4.3 billion in safety improvements nationwide over the next three years under the National Land Transport Programme to help save lives.
