Simon Greenwood claims to be 'very careful and experienced' motorcyclist in trial following partner Nikki Gapes' death

Simon Greenwood is on trial for careless driving causing the death of his partner Nicola (Nikki) Gapes. Photo / Supplied

Auckland businessman Simon Greenwood has claimed to be a "very careful and experienced" motorcyclist who had ridden the state highway where he crashed into a car at least eight to 10 times.

"There's many opportunities to overtake on that road, and the one I chose was perfectly safe … all [the driver] had to do was look," Greenwood said at his trial for careless driving causing the death of his partner, Nicola (Nikki) Gapes.

Greenwood had attempted to overtake a line of southbound traffic on Kaipara Coast Highway in the northbound lane, Gapes in pillion, in January 2018.

A car was turning right into Mangakura Boat Club and the two vehicles collided. Gapes died at the scene. Another motorcyclist and Greenwood were seriously injured.

Greenwood said he was "just cruising" home and "wasn't in a hurry" but a line of cars in front of him were going slower than the speed limit.

"They weren't frustrating me. They were going slowly and I was able to get past them easily, quickly and safely," he said under cross-examination by Sergeant Paul Nightman.

Mother-of-three Nikki Gapes, 43, was killed in this January 2018 crash near Mangakura Boat Club on the Kaipara Coast Highway. Photo / Auckland Rescue Helicopter Trust

Greenwood was travelling 90 to 100km/h when overtaking and he didn't notice the cars in front of him start to brake, or the turning car indicate, he said.

"He may have indicated as I was overtaking.

"An indicator is not a force field, it doesn't mean you can turn it on and pull out into oncoming traffic."

Greenwood asked a first responding officer at the scene if the driver - Rena Kipa - had indicated, then said a string of expletives, the court heard in evidence yesterday.

"I don't recall that conversation," Greenwood said today.

"I was concussed. I'd just have a massive accident ... so expletives coming out of my mouth are perfectly natural."

Greenwood said it's the "duty of care of other road users" to see him.

"People just can't pull out in front of you as you're overtaking because if that happened there would be a lot of collisions on the road.

"I noticed that traffic was moving slowly. The road markings had changed to allow overtaking. I saw that there no cars coming towards me and so ... it was clear to pass," he said.

He claimed his reaction time before braking was "less than a second".

"I slammed on everything I could and wasn't able to stop in time and rode into the back of the car.

"I used my front and rear brakes to stop the bike as hard as I could."

He was hospitalised for days with broken ribs, bruising, concussion and a broken spleen.

A road crash analyser called by defence counsel Blair McGregor said Greenwood would have had a "sufficient" view of the northbound lane before pulling into it.

"Neither motorcycle could avoid Mr Kipa's vehicle when it came into the lane," he said.

McGregor conducted a simulation to determine how easily it would be to see a motorcycle in the rearview mirror of Kipa's car, or any car, and determined it was "probable".

But Nightman poked holes in its similarity to the crash, such as the use of a different car, motorbike and location.

A senior constable who penned the crash analysis agreed the driver of the turning car did not check for traffic behind him before pulling off the highway.

"He had an obligation to check and make sure the way behind him was clear ... didn't he?" Greenwood's lawyer David Jones QC asked Karl Bevin under cross-examination today.

"Yes," replied Karl Bevin.

"Clearly he can't have done that," said Jones QC.

"Clearly," someone said loudly in the public gallery, to which Judge Michael Crosbie told them it was "completely disrespectful to interject".

"He clearly didn't do it, did he?" Jones QC persisted.

"No," said Bevin.

The driver of the car, Rena Kipa, has not been charged.

Kipa did not mention checking behind him before turning in his police statement, but while giving evidence yesterday claimed he looked around four times.

The actions of all those involved in the crash happened "in a very small space of time", Bevin said.

"We're not talking across a minute or half a minute, we're talking seconds.

Bevin agreed the two motorcyclists - who were not known to each other - were carrying out a "perfectly legal" manoeuvre when overtaking the holiday traffic due to the road markings.

Greenwood, 52 at the time, and Gapes, 43, were allegedly "ducking in and out" of traffic on his Kawasaki ZX on their way home to Auckland from a romantic long weekend in Russell.

The public gallery was packed with friends and family of both Gapes and Greenwood, some audibly sobbing when hearing evidence that Gapes was flung at least 18 metres from the motorbike.

Judge Michael Crosbie has reserved his decision.

To finish the trial Crosbie acknowledged Gapes' family in the courtroom, and how "upsetting and raw" the situation can be.