A specialist says a woman who drove a long distance while sleeping was probably unaware that she was falling in and out of sleep.
Police say the woman, who had taken sleeping pills and has a sleep disorder, drove from Hamilton to Mount Maunganui via Auckland just after midnight on Tuesday. She was also found to be texting.
A concerned friend alerted police, telling them the woman had just left her home in Hamilton. Her movements were tracked to her former address in Mount Maunganui, where she was found slumped over the wheel of her car and told officers she couldn't remember the four-hour drive.
Police are seeking an urgent order to forbid her from driving while she gets medical advice.
Alex Bartle from Sleep Well Clinics says the woman was most probably suffering from microsleeping, which can go unnoticed by those who do it. Dr Bartle said it is caused by extreme fatigue, which in this case seems the most likely situation.
Another sleep specialist, Dr Tony Fernando from Auckland University, says the woman's medication could have triggered sleep driving, allowing a person to operate a vehicle without having any recollection.
Traffic lawyer Steve Cullen say being asleep while driving can be used as a defence in court and likens driving while being asleep to being hypnotised.
Mr Cullen said cases like this come up only two to three times every 20 years and would be surprised if she is charged.