A woman who texted her friends and drove more than 300 kilometres - while on medication and half asleep - could be back on the road despite urgent police measures to try and stop her.
The woman was found by her cousin slumped over the wheel of her car just before 5am yesterday in the driveway of her old Bay of Plenty home - nearly five hours after she left Hamilton.
She drove about 110km north to Otara and going by police records, which placed her in South Auckland about 2am yesterday, would have needed to drive at 100km/h to reach Te Puna by 3.45am before she stopped at Mount Maunganui.
Police yesterday forbade the woman from driving for 12 hours as her medical condition and suitability to hold a driver's licence were assessed.
Waikato police communications manager Andrew McAlley said it was too early to know if the slumbering motorist would be facing any charges.
It was also unclear whether police would be filing an injunction through the courts to further stop the woman from driving, despite revelations her early morning trip was the second time she had sleep-driven in less than a year.
Senior Sergeant Dave Litton said police were first alerted when one of the woman's friends made a 111 call shortly after midnight telling them the woman had taken sleeping pills and had driven off from her home. "The woman's friend reported the driver had a sleeping disorder and had previously driven off while asleep 10 months ago, ending up in Tauranga," he said.
Mr Litton said police established the woman's cellphone was on, and she was texting as she drove, but those receiving her messages believed she was half asleep.
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"Her phone polled in Otara in Counties Manukau about 2am but the vehicle had gone when police arrived and the next message we received was that she was now heading for the Coromandel," he said.
About 3.45am the woman's phone polled in Te Puna near Tauranga before her car was found up a driveway at her former address in Mount Maunganui about 4.55am.
"When woken she had absolutely no recollection of the events overnight and we have sought an urgent order forbidding her to drive and to seek medical advice on her suitability to remain holding her driver's licence," said Mr Litton.
"While her being found safe and well is a relief for everyone involved, the potential for tragedy was huge and we're urging people suffering medical conditions to be open and honest with their doctors and seek advice on if the medication they are prescribed affects their ability to drive or not.
"Safer journeys being everyone's responsibility isn't just a slogan. It's an obligation we all take when getting behind the wheel. Last night's events could have so easily ended in tragedy which is something I am sure, we all want to avoid."
Sleep Well Clinic director Dr Alex Bartle said there were a number of factors that could have contributed to the situation but he believed it was likely a case of microsleeping, which is a very short nap usually caused by extreme fatigue.
He said there was evidence to suggest some types of sleeping tablets could lead to strange, automatic behaviour.
"Doing that sort of distance she would most likely be awake, just not thinking straight, and definitely microsleeping."
But NZ Brain Research Institute's Professor Richard Jones, who is conducting a study on the issue, disagreed saying microsleepers were totally non-responsive.
"My take on it is that she's a severe sleep walker," he said.
"The point is, she did drive safely 300km so she was clearly quite responsive. She could perceive the road conditions and she could respond to that.
"I've never heard anything quite like it. I'm quite intrigued by it."
Legal expert Warren Brookbanks said there were a lot of different elements in this woman's case, but police would generally have to seek licence suspension through the courts.
The courts would then decide her fate, based most likely on whether they thought the woman knew she was impaired but drove anyway, or if the entire journey was completely involuntary.