Roadside drug testing starting within weeks will check motorists for commonly prescribed medicines including Valium and sleeping tablets, as well as illegal drugs.
The Department of Transport has confirmed testing will be introduced in March, which will involve gardaí subjecting motorists to random checks using a portable device.
Motorists found to have levels above legal limits will be taken to a garda station and be obliged to provide a blood sample. Failure to comply constitutes an offence which can incur a fine of up to €5,000 and six months' imprisonment.
The machines will test for three illegal drugs - cannabis, cocaine and heroin - but more can be added over time. And the machines will also test for the presence of benzodiazepines which include Valium, sleeping tablets and other anxiety-treating medication.
If the driver has levels of the drugs above specified limits, they face a year's disqualification. A second offence means a two-year disqualification. Experts insisted that motorists on prescription drugs had nothing to fear as long as they took the prescribed dose, adding that medical exemptions will also be in place for medicinal cannabis, which is prescribed under the name of Sativex.
"If someone is taking them, in accordance with their prescription, there's no difficulty," said Professor Denis Cusack from the Medical Bureau of Road Safety (MBRS). "We know that many people are not taking benzodiazepines in accordance with the prescription, or are buying them on the black market."
He made the point that the emphasis was on road safety, not whether a drug was legal.
"There's an emphasis on impairment, or people taking things they shouldn't be taking. This is about road safety. There's the proverbial young man who goes to Amsterdam, takes cannabis where it's legal, and comes back. We also look at the young man who goes to Amsterdam and drinks . . . it's about when you get into your car, do you have something in your system which makes you unfit to drive?"
But in relation to prescription medication, he warned: "If in doubt, don't drive, and talk to your doctor or pharmacist. It could be your medical condition that needs to be checked."
Gardaí will not actually have to prove the driver is unfit to drive under the new system. If levels above permitted limits are detected in the blood test, it constitutes an offence.
Roadside testing is in place in a number of other countries including Australia, Belgium and France. A machine called a Dräger DrugTest 5000 will be used, which involves the motorist taking a sample of saliva using a swab. The swab turns blue when a sufficient amount is collected, before being placed in the machine. The result is available within eight minutes.
If it is a positive result, the motorist is taken to a garda station where a blood sample is taken. If this confirms the result, they will be prosecuted.
The new rules are being introduced under the Road Traffic Act 2016 and portable machines will be rolled out gradually, with 50 in the coming weeks - 86 will be available in stations, where tests can also be conducted.
Nearly 70pc of positive drug samples tested by the MBRS are in drivers under the age of 34.
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