HAND-HELD DEVICE DETECTS IMPAIRED DRIVERS

Graham Lawton Exclusive from New Scientist Print Edition.

A hand-held device designed to identify drivers impaired by drugs,
alcohol or excessive tiredness, is being evaluated by the British police.

The device is intended to deliver a quick yes or no verdict on whether
a person is in a fit state to drive and works by assessing the
driver's behaviour, rather than testing for particular substances. It
is the first of its kind to be tested by police anywhere in the world.

The "impairment detector" is still in the early stages of development,
but the Police Scientific Development Branch (PSDB) in St Albans,
Hertfordshire, is studying results from a prototype to decide whether
to take the project further. If it gets the go-ahead, at least two
years of testing will be needed before the detector is ready for the
streets.

"Early results are very promising," says Julia Boyle of the University
of Surrey in Guildford, UK, who is leading the research on behalf of
the PSDB and who revealed the results last week at a conference at
Cranfield University.

Twin Test

Boyle's prototype runs on a PDA. It provides two tests, which take
about 10 minutes to complete, and assess whether a person is too
impaired to drive (see Unfit to drive?" below).

Her team tested the prototype at two music festivals this summer,
where people who will admit to being impaired are relatively easy to
find. With 170 volunteers, the researchers found a significant
difference in performance between people who said they had not taken
drugs and those who admitted to being under the influence.

The main purpose of the device is to detect people who are unfit to
drive because they have taken illicit drugs, Boyle says. This is a
growing problem in the UK, where 18 per cent of road casualties in
2002 were found to have traces of drugs in their bodies, compared with
just 3 per cent 10 years ago.

The detector would deliver a verdict similar to the way a breathalyser
indicates how much alcohol is in the blood, with positive, negative
and a grey area between the two. Thresholds for these levels have yet
to be set, says Boyle.

Lingering Traces

As well as helping to screen people at the roadside, the test could
help to solve some of the problems that arise from testing for traces
of drugs in a driver's body. Cannabis, for example, lingers in the
body long after its effects on behaviour have faded.

This allows drivers found to have residues of the drug in their blood
to argue in court that they were not impaired at the time of driving.
And with so many illicit drugs in common use, it is hard to devise a
test that could pick them all up. Performance enhancing drugs do not
enable impaired drivers to beat the test, says Boyle.

A spokesman for the UK home office says it is too early to comment on
how such a device would be used or whether the results it produces
would be admissible as evidence in court.

UNFIT TO DRIVE?

The prototype impairment detector runs two tests designed to assess
three critical driving skills: motor control, ability to react to the
unexpected, and concentration levels.

In the first test, volunteers are asked to use a stylus to track an
object moving across the screen of a PDA, while every so often another
object pops up in the corner of the screen. When that happens, the
volunteers are required to press a button while continuing to track
the moving object. This test assesses the subject's ability to perform
a motor control task while their attention is diverted by unexpected
events.

In the second task, road signs flash up on the screen every second.
The driver has to respond to each of them, except a "target" sign that
they have been told about at the start of the test. When the target
flashes up they must not respond. This is known as a "sustained
attention" task, and measures a person's ability to
concentrate.

The tests were chosen from a wider battery of tests developed at the
University of Surrey, UK, to assess the effect of drugs and sleep
deprivation on people's ability to drive safely.