1,500 drivers tested positive for drugs in their systems last year and drug-driving is on the increase, a seminar to mark the beginning of Road Safety Week heard today.

Professor Denis Cusack of the Medical Bureau of Road Safety said the main drugs detected were cannabis, valium-like drugs and cocaine.

He said drug use, including some prescription drugs, impairs driving and judgement skills.

So far this year 164 deaths have occurred on Irish roads.