One in seven drivers have admitted falling asleep while driving, according to research carried out for the Road Safety Authority.
Most drivers attempt to fight fatigue by ineffective means such as opening a window, stretching their legs or turning on the radio, the research also found.
Launching a year-long campaign on the dangers of driver fatigue, the RSA today described it as a "silent killer" which may be responsible for over 350 road deaths over the past five years.
To mark the new initiative, Topaz service stations around the country will be handing out 20,000 free coffees to drivers on Good Friday and Bank Holiday Fridays, while Gardaí checkpoints will enforce safe driving over the Easter weekend.
RSA chief executive Noel Brett said scientific studies showed a motorist who drives while fatigued is as dangerous as someone driving at or above the drink driving limit.
"In a collision, you can test for alcohol or drugs or non-seatbelt wearing but you can't test for fatigue," he pointed out.
Mr Brett said anyone could experience fatigue while driving, but professional drivers, especially long-distance truck drivers, and long-distance commuters were particularly at risk.
The RSA survey of 800 motorists found 14 per cent of people nodded off when driving, with men between 35 and 54 years most likely to fall asleep.
Half of all incidents occurred between 9pm and 6am, with one in five cars drifting out of its lane of traffic. Of those who admitted to falling asleep, almost one in four said it had happened at least twice in the past year.
If a driver has a micro-sleep for just four seconds while travelling at 100km/h, the car will move 111m with no control.
Mr Brett advised tired drivers to stop, take a caffeine drink, have a 15 minute nap and then a short walk.
Garda Chief Superintendent Gabriel McIntyre said 1,000 members of the Garda Traffic Corps would be out in force over the Easter holiday to tackle reckless drivers speeding, taking drink or drugs or not wearing seatbelts.
"Every accident is one too many and this particular weekend we will have a lot of extra resources," said Supt McIntyre, of the National Traffic Bureau.
"We are out to ensure that people can start their journey and end their journey safely.
Two people were killed on Irish roads last Easter, while eight people died over the recent St Patrick's Day weekend.
