Motorists could face roadside drug tests under plans to reduce the number of drivers getting behind the wheel while intoxicated.
Police could be using a device within the next two years to detect illegal substances in saliva.
With random breath tests for alcohol already being considered by the Government, spot checks for illegal substances could also be introduced.
Ministers are hoping the new equipment will help them tackle the growing menace of “drug-driving”.
In addition to their own drug detector, the Home Office will also announce a deal in the next fortnight with a private contractor to develop a roadside device that is also capable of detecting legal drugs, such as sleeping tablets, which can impair driving.
At present, officers can stop a motorist who they believe may have taken drugs.
The normal procedure is to carry out a “field impairment test”, which measures co-ordination by a variety of exercises including standing on one leg, walking in a straight line and counting out 30 seconds. A motorist who appears incapable of performing these tasks faces arrest.
The driver is taken to a police station where a police surgeon takes blood samples after agreeing that the motorist seems impaired. The results of these tests lead to a prosecution.
The Home Office, which regards the present roadside co-ordination tests as crude, believes that technology will provide more accurate results.
Its scientists have been working on a device which can detect a number of drugs, including cocaine and amphetamine, in saliva.
It is understood to be near completion and ready to be brought before international experts for verification.
A motorist failing a “drugalyser” would automatically be taken to a police station for a blood test.
The extent of drug-driving is difficult to estimate, but in 2005, the last year for which figures are available, 363 motorists were convicted of driving while under the influence of drugs.
Another 28 were found guilty of being in charge of a vehicle while impaired through drugs.
However, it is believed that these figures grossly underestimate the number of drivers who get behind the wheel after taking illegal substances.
A Scottish Executive survey of drivers aged 17 to 19 found that nine per admitted having taken drugs in the previous 12 months. Six per cent admitted having driven while under the influence.
“Recognising drug-driving is a big problem,” said Robert Gifford, of the Parliamentary Advisory Council for Transport Safety.
“Firstly we don’t have the technology which can identify all drugs. Also drivers who are under the influence will often try to disguise it by having a small amount of alcohol.
“That means that when they are stopped and an officer smells alcohol, they take a breath test, which they pass.”
Even with a Government-approved drugalyser, other obstacles remain.
There is no legal limit for drug use, but setting a zero level could present other problems.
While cannabis can stay in the blood for several weeks, a defence lawyer could argue that an illicit joint smoked a fortnight previously could not be held to have had any impact.
For more information about drug driving or driving whilst unfit, please visit our dedicated page detailing the services we offer to those facing prosecution for this offence.
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