A study into drug use by motorists has found that of 2,000 specimens analysed by the Medical Bureau of Road Safety, 15.7 per cent were positive for one or more drugs.
The findings, to be published today, was carried out in conjunction with the Department of Public Health Medicine & Epidemiology at University College Dublin.
The samples, taken from motorists suspected of driving while under the influence, were analysed for seven drugs or drug classes. Of these, 1,000 were under the limit for alcohol and 1,000 were over the limit.
It was found that of the samples taken from drivers with very low or zero levels of alcohol, 67.9 per cent were positive for drugs.
Cannabis was the drug most commonly found in six out of 10 drivers who tested positive. Of the samples taken from drivers under 25 years of age, 24.9 per cent were positive for drugs, while 19.4 per cent of the 25 - 34 year olds were positive.
According to the Medical Bureau of Road Safety, the survey highlights the need for education and awareness in relation to drug use by motorists.
The study concludes that: "there are immediate implications for the Evidential Breath Testing Programme. In the event of a nil or low alcohol being obtained, the Garda should be aware of the significant likelihood that the driver's impairment may be due to the presence of a drug or drugs other than alcohol."
The Government's upcoming Road Safety Strategy, due to be published in the coming weeks, sets as one of its targets that suspected drink drivers who pass the breath test will be tested for drugs by officers specially trained in drug-use recognition.
The study supports recent figures from the North's Department of Environment and PSNI which show a quarter of all drivers and motorbike riders killed on Northern Ireland's roads last year were positive when tested for drugs.
The extent of the drugs problem was disclosed by figures in the North which showed that since the start of 2001 tests have been carried out on the bodies of 187 dead drivers and riders, and 44 tested positive for drugs.