KEY POINTS:
Transport psychologist Samuel Charlton advocates a zero alcohol limit for drivers.
Dr Charlton, a member of Waikato University's traffic and road safety research group, says the current limit of 80mg per 100ml of blood is much higher than most people realise.
"It's hard to get up there if you try to do it," he said. "And most people will tell you that when they're at that point, no, they're not fit to drive."
He said research showed that "automatic procedures" - "the stuff that gets us home when we're not thinking about it" - were the first aspect of driving to deteriorate after alcohol.
"Those procedures are impaired even before the ones that interfere with our ability to carry on a conversation or do things consciously."
Automatic procedures included driver speed, distance maintained from the car in front, lane position, and the approach to a familiar intersection.
"That's exactly what alcohol interferes with first, and you can't rely on it to get you home safely from the pub," Dr Charlton said.
He said a zero alcohol limit would prevent drivers having to ask themselves, "Have I had too much or haven't I?"
"The reason I advocate zero is not because I think people are incapable of handling a drink or two. It's because now you're putting them in the position of guessing whether or not they can handle it, whereas if it's zero, it's really easy to tell."
Dr Charlton acknowledged that a zero limit would be difficult to introduce in New Zealand because of a lack of public transport, but said pilots had a zero limit and some drivers, including himself, already followed an "internal self-policing limit of zero".
"Even me, a road-safety guy, can't tell when I'm impaired because we drive on automatic pilot. You won't notice."
He believed lowering the blood alcohol limit from 80mg to 50mg would also be problematic.
"Unless it's accompanied with good public education about why, it's going to be difficult, just the same way as we've got very wide straight roads and it's difficult to convince people they should go 100km/h on them."
In 1998, the police commissioner of the day, Peter Doone, led a push for a zero limit. He resigned in 2000 after the Police Complaints Authority found he had acted undesirably when a vehicle driven by his partner was stopped for a breath test.
www.nzherald.co.nz/roadsafety
