Five people have been killed in separate road crashes since Friday evening.
The five men died in collisions in counties Waterford, Roscommon, Kerry, Louth and Limerick between Friday and today.
Two of those who died have been named.
One was musician Chris Bradley, who was a passenger in a car that collided with a tractor at Mooremont, Co Louth.
The other was 21-year-old pedestrian Joe Drennan. The journalism student was killed when when two cars collided in Castletroy, Co Limerick on Friday night.
In a statement tonight, the Garda Síochána Ombudsman Commission said it was investigating the incident.
Country singer Declan Nerney has said he is "devastated" after Mr Bradley's death.
In a post on social media, Mr Nerney said: "Chris was a magnificent drummer and above all that an even better colleague and friend. He was the life and soul of the party, always lit up a room with his great sense of humour and a powerful legion of fans."
Meanwhile, the President of the University of Limerick paid tribute to Mr Drennan.
Kerstin Mey extended her sympathy to his family and all of his "journalism classmates and lecturers, to his housemates, friends and fellow UL students and the many others who will be so devastated by his loss".
Mr Drennan was in his fourth year in Journalism and Digital Communication and was also Editor-in-Chief of the Limerick Voice newspaper.
Assistant Professor and course director Dr Kathryn Hayes said: "We are absolutely devastated in the journalism department and in the wider UL community to learn of the tragic death of our student Joe Drennan. Our heartfelt sympathies are with Joe's family at this terrible time and all of his classmates and many dear friends.
"Joe was an inspirational student and a hugely talented young journalist, who had a bright career ahead. He was passionate and creative and will be sorely missed by all of us who had the pleasure of knowing and working with him," she added.
Minister for Higher Education Simon Harris also paid tribute on social media saying he sent his sympathies and thoughts to all at UL and to Joe Drennan's family and friends.
"I know the university community is grieving and we grieve with them at this very sad and difficult time," he added.
Three motorcyclists also died in separate road crashes in Co Waterford, Co Roscommon and Co Kerry.
A man in his 70s died in a single vehicle collision involving a trike in Co Waterford.
He was pronounced dead at the scene following the crash on the Chapel Road in Stradbally at around 12pm today.
The scene of the collision has been preserved for a technical examination by garda forensic investigators with the road closed and local diversions in place.
Gardai are appealing for anyone with information, particularly those travelling on the road between 11.30am and 12.30pm today to contact Tramore garda station on 051 391 620, the Garda Confidential Line on 1800 666 111 or any Garda station.
The crash in Co Roscommon happened on the R357 between Shannonbridge and Ballinasloe in the townland of Cloneish.
A man in his early 30s was driving a motorcycle which collided with a car at around 5pm yesterday evening.
The motorcyclist was taken to hospital where he was pronounced dead a short time later.
No one else was injured in the crash.
The third motorcyclist, a man in his 40s, was killed after a collision with a van at Moyvane North, Listowel, Co Kerry at around 7pm yesterday.
The man was pronounced dead at the scene.
The driver of the van, a man in his 70s, was taken to University Hospital Kerry for treatment to injuries believed to be non-life-threatening.
The scene of the collision is preserved while Garda Forensic Collision Investigators conduct a technical examination. The road is currently closed.
Gardaí in Listowel are appealing to anyone who may have witnessed the collision to contact them.
Any road users in the area of Moyvane North between 6.15pm and 7.15pm yesterday, and who may have camera footage (including dashcam), are asked to make this available to gardaí.
Anyone with any information should contact Listowel Garda Station on 068 50820, the Garda Confidential Line on 1800 666 111 or any garda station.
This weekend's fatalities bring the number of people who have been killed on the country's roads to 149 so far this year.
It is estimated to be 34 more than were killed in the same period last year.
Last year a total of 155 people died in fatal road collisions.
