Fewer people died on the State's roads last month than in any previous May since 2002, according to the Garda.
The Road Safety Authority (RSA) attributed the lower death toll to mandatory alchohol testing.
A total of 21 people were killed in May, compared to 31 in the same month in 2006 and 51 in 2005. It is the lowest total since May 2002, when there were 20 deaths recorded.
Four people died over the June Bank Holiday weekend, a decrease from seven over the same period in 2006.
In total, 142 people have been killed on Irish roads since the start of the year. This is 34 fewer than last year.
The Road Safety Authority said today the number of roads deaths has dropped by 23 per cent since mandatory alcohol testing was introduced last July.
"Over the last eleven months there have been 274 deaths on our roads while the previous eleven months saw 354 deaths," said RSA chief executive Noel Brett. "It is clear that mandatory alcohol testing has contributed significantly to the number of lives saved - along with high profile awareness campaigns and a greater Garda presence on the roads."
Mr Brett said new HSE research shows alcohol was a factor in 36.5 per cent of fatal crashes, rising to 62 per cent in single-vehicle, single-occupant fatal crashes. In 89.7 per cent of crashes attributable to drunk driving, the driver was male.
Some 372 people were arrested for suspected drink driving over the weekend. Supt Kevin Donohoe of the Garda Press Office noted this is the same as the corresponding figure in 2006, despite a significant increase in enforcement.
"This would tend to indicate that the message is getting through to people and more and more drivers are complying with the law and advice," he said. "It is the objective of An Garda Síochána to continue to increase this compliance culture with the ultimate aim of reducing the number of deaths and serious injuries on our roads.
"It is not our intention to catch people out or increase revenue but simply to continue to get road safety messages across to the public to make Irish roads safer for everybody," he added.
