Some 100,000 motorists have been breath-tested since random alcohol tests began in July, Garda Commissioner Noel Conroy said yesterday.
Of these, 2,700 or 2.7 per cent were arrested for being over the limit, while 20 drivers refused to take the test.
Mr Conroy told the Oireachtas Committee on Transport that legislation allowing for random testing had proved "extremely beneficial" to gardaí and the public.
"We're extremely happy with the random alcohol-testing legislation. In the past, people who had consumed alcohol but could persuade a garda that they were not impaired could slip the net," he said.
He warned that while the figures showed the extent of Garda enforcement of the traffic laws, they were also an indication that "a culture of drink-driving still exists, in spite of our enforcement and the media and educational campaigns conducted with our partners in road safety".
There have been 310 people killed on the State's roads so far this year, 12 fewer than the corresponding period in 2005.
"While there has been a decrease in the rate of road fatalities, it is too early to say if there is a trend, or if the reduction is due to random alcohol-testing," he said.
Meanwhile, Mr Conroy is to circulate a directive advising members of the force that all drivers involved in road collisions should be tested for alcohol.
Current legislation states only that those involved in crashes may be breathalysed at the scene of an incident, but Mr Conroy said all drivers should be tested.
"Clearly we have talked about this around the management table. We have said that we shouldn't be looking at the word 'may'. We should just go out and do it. I would expect that guards would be doing this, and we will be sending out a directive that that should happen to everyone who is involved in a collision."
If a driver is brought to hospital, the decision to carry out a test shall remain at the discretion of individual gardaí.
Responding to questions on the problem of so-called boy racers, Mr Conroy said officers had recently found that some young people were using mobile phones to alert friends to the presence of Garda checkpoints.
"People are using mobile phones, talking to each other and telling people that checkpoints are set up," he said.
"More and more unmarked cars will be going out there before Christmas to catch those individuals."
Separately, the committee heard that a pilot drug-testing scheme introduced in the Australian state of Victoria in 2004 found that one in every 46 motorists tested positive for illegal drugs such as cannabis and amphetamine, compared to one in 250 for excessive alcohol.
Chief executive of the Road Safety Authority Noel Brett said there was little data available on the significance of drug-taking in road collisions in Ireland.
But he added that future research would have to analyse the potential of prescription drugs as well as illicit chemicals to impair driving.