A learner driver clocked by police at 212km/h has pleaded guilty to illegal street racing.

Tepiwa Michael Peter Keremete Riwai, 32, appeared in the Hutt Valley District Court on Thursday and admitted a charge of operating a vehicle in a race or exhibition of speed, after a patrolling police officer detected him at speed on State Highway 2.

Riwai was driving a Holden Commodore about 9pm on March 8 with his partner, a restricted licence holder, in the car. He holds only a learner licence and was driving in breach of it, the summary of facts said.

Somewhere between Avalon and the Haywards Hill interchange in the Hutt, another Holden Commodore pulled up alongside Riwai's car.

The two drivers then accelerated north on the highway, with Riwai reaching the speed of 212km/h. The other driver allegedly reached 186km/h.

There were other vehicles on the road at the time.

A stationary police patrol spotted the two cars racing and pursued them, stopping Riwai near Silverstream and arresting him.

The other driver, 38-year-old Jason Leslie Campbell, was stopped a short time later in Upper Hutt and was also arrested.

Both drivers had their licences suspended for 28 days and their cars impounded.

Riwai told police he initially thought he recognised the other driver and wanted to get away from him.

But he soon admitted it developed into a race, and accepted what he had done was dangerous to the public and himself, the summary of facts said.

Campbell allegedly told police he was driving in convoy with Riwai, and that his car could not reach the speed he is accused of driving at.

He has pleaded not guilty to the racing charge and will reappear in court at a later date for case review.

Riwai, who has previous charges, will be sentenced on August 22 in the Hutt Valley District Court.

National road policing manager Superintendent Steve Greally last week said poor decision making was the main cause of crashes in New Zealand.

His comments came after the horror crash at Waverley in South Taranaki which claimed seven lives, including that of a baby and a young girl.

"I think the most common cause of crashes is poor decision making on behalf of our drivers out there. The drivers are the ones responsible for the decisions they make and how they're going to operate that motor vehicle, or how they're going to cross that road or how they're going to ride a push bike," Greally said.

Riwai's guilty plea comes a month after two "lunatic" motorcyclists were spotted riding at speeds above 300km/h south of the Rimutaka Range.

They were seen on June 2 travelling at 247km/h on State Highway 2, and upon realising they'd been seen, accelerated to more than 300km/h.

Upper Hutt mayor Wayne Guppy said the speeds the motorcyclists were going was "absolute lunacy".

In 2016 a learner motorcyclist was also caught doing a "suicidal" 232km/h while trying to flee police.

The rider was wearing shorts and had a suspended learner licence when his speed was clocked on a Waikato road.

Stu Kearns, former head of the Waitematā Serious Crash Unit, told the Herald at the time that 232km/h was a "suicidal speed" and was certainly among the highest he had heard of in New Zealand.

"A rider in shorts, even leathers, wouldn't survive an impact at that speed. All his bones and organs would be just mush by the time he came to rest."