One fifth of all fatal car crashes in Ireland are likely to have been caused by driver fatigue, according to the Road Safety Authority.
The body is launching a winter road safety campaign today specifically targeting fatigued motorists.
It says tiredness is just as dangerous as drink-driving and has contributed to 200 fatal accidents in Ireland over five years.
Safety Authority chief executive Noel Brett is appealing to motorists who feel tired to take a 15-minute break, drink two cups of coffee, have a nap and take a brisk walk before they resume their journey.
"We're particularly aiming this advice at shift workers, people with sleep disorders and particularly at young men," he said.
"When we have fatal and serious-injury collisions, they tend to be in the early hours of the morning, when fatigue may well be a factor."