The Road Safety Authority is appealing for drivers to make safe choices this weekend.
It comes after two young men and one 21-year-old woman died in a two-car collision on the outskirts of Letterkenny yesterday morning.
While a 26-year-old man was also killed in Co Galway yesterday.
The deaths bring to 12 the number of people killed on Irish roads since Sunday.
Brian Farrell, from the Road Safety Authority, said: “Please, please, please, slow down. It is a factor in a third of collisions, speed.
“But equally, alcohol is also a big problem out there, also counting for 38% of all fatal crashes that are taking place on our roads.
“So we need people to make the right choices, to make sensible choices this weekend.”