Paula Nicolle, 61, was killed when her Suzuki hatchback collided with a Subaru station wagon on Kimberley Road on Saturday, July 27 last year.

The Subaru was being driven by Gianna Lacey who was travelling with her son Liam.

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Both Ms Lacey and her son survived but were taken by ambulance to hospital.

In a report, Coroner Simon Cooper said the crash occurred when Mrs Nicolle exited a right hand curve and did not steer out of it, and so entered the incorrect lane.

"Investigations indicate neither vehicle took any form of evasive action prior to impact," Mr Cooper said.

The coroner said a pathologist determined Mrs Nicolle died from multiple blunt traumatic injuries which included an injury so severe it would have led to "near instantaneous death".

He said he could not determine why Mrs Nicolle's car crossed into the incorrect lane and the path of Ms Lacey's vehicle.

The coroner ruled out speed, weather, drugs, alcohol, existing health issues and mechanical failure as potential causes of the crash.

Mr Cooper also found that Mrs Nicolle was "rested and happy" prior to the crash, and so ruled out fatigue.

"Similarly, there is nothing to suggest that Mrs Nicolle's vehicle moving into the incorrect lane was an act done by her voluntarily," he said.

"Thus, suicide can also be ruled out in this case."

The coroner said she was driving under the posted 100km/h speed limit, between 75km/h and 85km/h, and that she was wearing a properly fitted and adjusted seatbelt, and that her airbag deployed.

There were only four minor crashes on the same stretch of road in the five years prior to Mrs Nicolle's death, Mr Cooper said.

He concluded that the crash was likely the result of Mrs Nicolle's inattention but he could not determine, on the evidence provided, why her car crossed into the incorrect lane and the path of Ms Lacey and her son.

Mr Cooper said no recommendations or comments were necessary, thanked police crash investigators and conveyed his condolences to Mrs Nicolle's family.