The new Road Traffic Bill will provide for roadside impairment tests to detect drug driving, the Minister for Transport Leo Varadkar has said.
Under the measure, gardaí could request drivers to perform cognitive tests such as walking in a straight line, tipping one's nose or counting while standing on one leg to determine whether the driver has taken drugs.
A report published today by the Medical Bureau of Road Safety (MBRS) recommended the tests amid a "year-on-year increase" in drug driving.
Gardaí will target drivers who have consumed illicit drugs or who have taken prescription drugs without the advice of a doctor.
Mr Varadkar said implementing the impairment test recommendation was "just now a case of passing legislation and commencing it."
"We anticipate publishing the [Road Traffic] Bill… at the end of the year and I expect to bring it through the Dáil and Seanad in the first session of next year."
Drivers who take prescription medicines in accordance with their doctor or pharmacist's advice have "nothing to be afraid of, nothing to be nervous of," said MBRS director Denis Cusack.
More than 3,000 gardaí have been trained in the use of these impairment tests, on top of which the MBRS is also looking at introducing devices, similar to breathalysers, to detect the presence of drugs in a driver's system.
"How to detect the drugs is a much more complex issue than it is with alcohol… Drugs don't go into the breath as easily as alcohol. We have a breathalyser and evidential breath testing for alcohol but it's not that easy for drugs," Mr Cusack said.
"While research in this area is continuing, oral fluid is emerging as the specimen of choice for use in roadside chemical drug testing devices," he added.
MRBS estimates the costs of oral fluid roadside tests at between €15 and €20 per test, or "between 60 and 125 times more expensive" than the cost of breath alcohol tests.
Unlike drink driving, a driver can only be prosecuted for drug driving if they show visible signs of impairment and if a subsequent blood or urine sample returns a positive result for a drug.
Mr Cusack said international evidence suggests a zero-tolerance approach to drug driving is most effective.