Driving worse as blood booze levels drop

Last updated 08:49 04/12/2013

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Waiting an hour or so to drive after you've guzzled a few glasses of bubbles at the Christmas party may prove more deadly than jumping behind the wheel straight after you've knocked them back, a new study shows.

Associate Professor Samuel Charlton and Dr Nicola Starkey from Waikato University's School of Psychology recently completed a large research project that revealed drivers are extremely poor judges of their own sobriety and that the same amount of alcohol in the blood can have different effects, depending on how long it has been since you started drinking. The most astonishing thing they found was that as blood alcohol levels were declining, the ability to manoeuvre a vehicle worsened. The study also discovered that the longer you waited after having a drink, the harder it was to determine just how drunk you were.

"Your perceptions of how drunk you are, are a lot more accurate when your blood alcohol levels are increasing as opposed to decreasing," Dr Starkey said.

The study involved participants consuming drinks of varying alcohol quantities while their driving skills were tested in a simulator. Participants were not told how much alcohol was in their drinks. The participants' simulation test involved swerving around a reversing car, and those who had decreasing blood alcohol levels spent a lot more time across the other side of the road than those who had just hit the sauce and driven, Dr Starkey said.

Although there were many factors that could lead to this - the study could not pinpoint a single reason - it was important that people were aware of the dangers of declining blood alcohol levels, the researchers said.

"After a while, the participants felt like they had ‘sobered up' enough to drive, even though they had as much alcohol in their blood as before. The really dangerous thing is that although they felt better, their driving and cognitive performance was significantly worse than before," Dr Charlton said.

The research project was produced for the Government to assist in the decision to lower the legal limit for New Zealand drivers from the current level of 0.08 BAC (blood alcohol concentration) to 0.05 BAC. The project follows on from a series of studies carried out by Dr Charlton and his colleagues at the university's Traffic and Road Safety Research Group, including self-explaining roads and driver awareness, the use of cellphones while driving, and a novice driver training and education programme.

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- © Fairfax NZ News

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