An off-road driver has admitted causing a crash 41m down a steep gorge that killed his girlfriend.

Campbell Thomas Klubein Page, 24, this morning pleaded guilty to a charge of careless driving causing death after the January 30 crash last year in Macetown, near Arrowtown in Central Otago.

Olivia Cait Brown, 22, of Lake Hayes, died when the vehicle she was a passenger in left a remote 4WD track and crashed 50m down a steep bank.

Page, a landscape gardener from Fendalton, Christchurch, suffered moderate injuries.

He was later charged and after originally appearing at Queenstown District Court, had his case transferred to Christchurch District Court.

Judge Stephen O'Driscoll said a summary of facts can now be released to the Herald before Page is sentenced on September 8.

On January 30 last year, the summary says that Page and Brown arranged to complete the Macetown off-road track in his 1987 Toyota Blizzard 4WD before using a small inflatable raft in the river.

Page had travelled the 4WD track, which crosses the Arrow River 23 times and takes about an hour each way depending on weather and conditions, once several years beforehand.

The Macetown track near Arrowtown is popular with 4WD enthusiasts. (Photo / Getty Images)

He advised Brown that seatbelts shouldn't be worn because the track was bumpy and they would strangle her.

Just after midday, Page met up with another 4WD vehicle with four others from out of town who were also completing the trip.

"A discussion was held between the two vehicles and there was an agreement to help each other out if necessary," the summary says.

At some point during the journey, the group navigated through an area above a dam on the Arrow River gorge.

After negotiating a tight bend, the Toyota's right-side wheels hit and went along a rocky piece of schist.

The 4WD dropped back down on all four wheels when it appears Page has lost control and over-corrected his steering.

"Due to not wearing his seatbelt, the defendant would not have had full control of the steering wheel during this time, being bounced around the cab of the vehicle," the summary says.

The vehicle left the track and rolled 41m down the gorge, ending in a 24m "vertical drop" which resulted in them "coming to rest against a large boulder".

"The victim Brown was thrown about within the vehicle unrestrained with her head colliding into the drivers' side pillar and other areas of the internal and external cab area," the summary of facts says.

"Brown suffered non-survivable head injuries and died at the scene a short time later."

Page was ejected from the vehicle "via the windscreen during the initial rolling" and received small cuts and grazes to his lower legs.

When he spoke to police, Page said that he "high-sided" the vehicle, "f***** up" and "tried to correct but couldn't".