The Road Safety Authority says as many as one in five fatalities on the roads are caused by driver fatigue.
The authority says crashes involving a tired driver tend to be more serious as the person behind the wheel does not react quickly enough to avoid the collision.
The body is appealing to motorists to take breaks on long journeys, and if they are feeling tired to take a break for a nap.
Ninety-two people have lost their lives on Ireland's roads so far this year.
The RSA's Brian Farrell said people do not take the issue seriously enough.
He said: "One in five fatal crashes could be attributable to driver fatigue and because the drivers are asleep at the wheel at the time of the crash, they tend to be high impact collisions because no avoidance action has been taken by the driver.
"Things like turning the volume up on the radio and opening the window - all these tactics don't work.
"The only cure really is that 15-minute nap, and if you can, get a cup of coffee."