A witness to the aftermath of a Northland crash that killed two people on Saturday says she has been warning about the dangers on the stretch of road for months.

Two other people, including a child, were also injured in the crash that closed both lanes of State Highway 1 at Oakleigh, south of Whangarei for more than five hours.

Denise Wilson, who saw emergency services attending to the victims from her Totara Road house, said the scene was "horrific".

"It's just horrific...and this comes after several other fatal accidents we've had."

Wilson said she had previously voiced concerns about the stretch of road, incuding writing to the New Zealand Transport Authority.

"There's a passing lane and the road is pretty narrow, and cars tend to speed up and it's so dangerous," Wilson said.

"The traffic volume has quadrupled since we moved here 11 years ago, and it's a stretch where accidents are just waiting to happen."

Wilson says the stretch needs to be turned into a four-lane highway.

Wilson and her husband Alan have written several emails to NZTA's Safe Roads Alliance with pleas to make it safer to turn on to State Highway 1 from their house.

"We have had a fatal accident on this corner and just yesterday there was a serious accident near the turn off onto Totara Rd," they said in an email dated January 23, 2018.

"There is a blind corner we contend with and passing lanes where speed is hazardous."

In an email response, community engagement manager Kathy Chinn acknowledged there "has been a history of crashes in the area".

Chinn said the analysis showed most of these resulted from loss of control due to people going too fast for the conditions.

She said the Safe Roads team was looking at lowering the speed limit and having a wider centre line to act like a buffer zone.

Nine months on, Wilson said none of these ideas had been implemented.

"How many more people need to die before any action will be taken?" Wilson said.

Saturday's crash is believed to have occurred near the passing lane.

The double fatality took the Labour Weekend holiday road toll to three.

A police spokeswoman said investigations by the Serious Crash Unit were ongoing. The names of the victims have not yet been released.

Meanwhile, motorcyclist Ethan Nathaniel Bishop, 18, died in a crash near Otorohanga on Friday night.

Police national road policing manager Superintendent Steve Greally is reminding drivers to keep safe on the roads.

"Drivers can keep themselves and others safe by paying attention to their driving and surroundings, driving to the conditions, never driving impaired and always wearing their seatbelt," Greally said.

"We know the four main behaviours that contribute to death and serious injury on our roads are people driving distracted,, drivers impact by fatigue, drugs or alcohol, drivers speeding and people not wearing their seatbelt."