Gardaí are to be trained to identify "drug-drivers" and will have the right to ask drivers to walk along white lines at the roadside and take part in other dexterity tests to determine their sobriety.

The Department of Transport confirmed that the Road Traffic Bill 2009 includes provisions for 'field impairment testing'.

"The Road Traffic Bill includes provisions for field impairment testing – non-technological methods by which the gardaí can make a preliminary assessment about the possible presence of drugs," said a statement.

The Medical Bureau of Road Safety (MBRS) at UCD is in talks with the gardaí about training selected gardaí to help them identify drivers under the influence of drugs.

"A group of gardaí will be trained at UCD and earn a qualification in field impairment testing. These 'garda trainers' will then train other gardaí on how to recognise when someone is under the influence of drugs," said Professor Denis Cusack of the MBRS. "Things like examining the size of people's pupils, examining people's balance and other dexterity tests like walking along the white line at the side of the road will all be part of it. It is most likely that traffic gardaí will be the first to earn this qualification and the course will begin next year."

One of the problems faced by police in combating drug-driving is the lack of a suitable roadside test. A drug-driving test has been piloted in Australia which tests for cannabis, amphetamines and ecstasy.

At present, gardaí must "form an opinion" that a driver is under the influence of drugs and take them to a garda station for a blood or urine sample.

The new legislation will also reduce the blood-alcohol limit for drivers and introduce mandatory alcohol testing for all motorists involved in accidents.