A warning to not underestimate just how dangerous New Zealand's roads are.

NZTA wants to slash speed limits around the country dropping to 60 kilometres an hour on some open roads.

It says 90 percent of roads are not safe enough for the speed limits they have.

WPUS OPus Technical Director, and former safety roads adviser for NZTA, Fergus Tate told Mike Hosking lowering speed is the best way to decrease the risk.

"If you're thinking about the total New Zealand road network of some hundred thousand kilometres, there's an awful lot of windy, torturous narrow roads with serious roadside hazards against them."

He says that some of our roads need major work as they are seriously dangerous.

"We're one of the many countries, but not one of the best countries, that uses a four inch paint line to separates traffic streams at 100 kilometres an hour."