Pubdate: Sat, 16 Dec 2000
Source: New Scientist (UK)
Section:  Page 6
Copyright: New Scientist, RBI Limited 2000
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Author: Arran Frood

DON'T BE A DOPE

If you're going to smoke a joint, don't drive home

IT'S official: smoking dope makes you a worse driver. But cannabis has less 
effect on driving ability than alcohol, according to a study by the 
Transport Research Laboratory (TRL) in Crowthorne, Berkshire.

The Department of Environment, Transport and the Regions asked the TRL 
Safety Department to investigate the effect of cannabis intoxication on 
driving ability. Cannabis is by far the most common illegal drug found in 
the bloodstream of road accident victims, and THC-the active ingredient in 
cannabis-can remain in the body for more than a month.

Barry Sexton and his colleagues at the TRL recruited 15 volunteers to 
complete driving tests while under the influence of low or high doses of 
cannabis, or no drug at all. The volunteers either smoked readyrolled 
cannabis joints or rolled their own with resin supplied under government 
licence. They were then put through their paces on a sophisticated driving 
simulator.

The researchers measured their accuracy at steering the car, known as 
"tracking ability", and other psychomotor responses, such as hazard 
perception and braking responses. They took blood and saliva samples at 
regular intervals and also tested the subjects' coordination, balance and 
timing.

The first thing the researchers noticed was that the subjects drove more 
slowly under the influence of dope, compensating for their intoxication by 
driving more cautiously. Tracking ability was the only test criterion that 
was adversely affected: the volunteers found it very difficult to follow a 
figure-of-eight loop of road when given a high dose. Reaction times to 
motorway hazards and performance on cognitive tests in the lab were not 
significantly affected.

Trials previously completed under similar test conditions at the TRL have 
shown that alcohol and tiredness have a more adverse effect on driving 
ability, affecting higher cognitive processes. The results of the cannabis 
and driving study agree with similar research carried out in Australia, the 
US and Holland.

Pete Henshall of the Legalise Cannabis Alliance, which is a British 
political party, comments that "any person who is not in full control of 
their body should not drive, be it through tiredness, alcohol, cannabis or 
drugs ... but everything must be seen in proportion. We need to legalise 
and regulate cannabis in a similar way to alcohol to be able to see the 
size of the problem."

Jane Eason of the Royal Society for the Prevention of Accidents favours the 
roadside  tests to spot cannabis intoxication now being tried by British 
police. "We would welcome any measure that might make the roads of Britain 
safer."
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