BBC Homepage World Service Education
BBC Homepagelow graphics version | feedback | help
BBC News Online
 You are in: Health
Front Page 
UK Politics 
Background Briefings 
Medical notes 
Talking Point 
In Depth 

Wednesday, 13 December, 2000, 20:53 GMT
Cannabis driving danger measured
Cannabis makes people drive more slowly
Researchers have confirmed that smoking cannabis can impair driving ability - but not as much as drinking alcohol.

The Transport Research Laboratory (TRL) in Crowthorne, Berkshire was asked by the government 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.

Any person who is not in full control of their body should not drive

Pete Henshall, Legalise Cannabis Alliance
The active ingredient, THC, can remain in the body for more than a month.

New Scientist magazine reports that the TRL team recruited 15 volunteers to complete tests on a sophisticated driving simulator while under the influence of low or high doses of cannabis.

The volunteers either smoked ready-rolled cannabis joints or rolled their own with resin supplied under government licence.

The researchers measured the volunteer's accuracy at steering the car, response to hazards and braking times.

They also took blood and saliva samples at regular intervals and also tested the subjects' coordination, balance and timing.

Slow driving

The most obvious effect of the cannabis was that the volunteers drove more slowly, trying to compensate for intoxication by being more cautious.

The volunteers also found it difficult to follow a figure-of-eight loop of road when given a high dose of cannabis.

However, reaction times to motorway hazards 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.

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, said: "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, supported trials currently underway of roadside tests for cannabis intoxication.

She said: "We would welcome any measure that might make the roads of Britain safer."

A spokesman for the Department of Environment, Transport and the Regions, which commissioned the research, refused to comment until the report is officially published.

Search BBC News Online

Advanced search options
Launch console
See also:

01 Dec 00 | Health
Grass keeps you calm on the road
20 Oct 00 | Health
Driving eye tests 'inadequate'
12 Dec 00 | Health
Cannabis clues to fertility
Internet links:

The BBC is not responsible for the content of external internet sites

Links to more Health stories are at the foot of the page.

E-mail this story to a friend

Links to more Health stories