Operation Slow Down is under way across the country, with gardaí and the Road Safety Authority urging motorists to stay within speed limits during the busy Christmas and New year travel period.
So far this year, 156 people have lost their lives on Irish roads, which is 28 more than on this day last year.
Operation Slow Down began at 7am with all divisional road policing units conducting speed checks across the country.
Between 7am and 9am, one driver was detected travelling at 135km/h in a 80km/h Zone on the N4 at Ballydowd, Lucan in Dublin, with another driving at 88km/h in a 50km/h Zone on the Coolock Lane in Dublin 17.
In the first five hours of the initiative, the speed of nearly 70,000 vehicles was checked, with 270 vehicles found to be travelling in excess of the speed limit.
One motorist was clocked at travelling 132km/h in a 100km/h Zone on the N4 Greatdown, The Downs in Co Westmeath and another clocked at 135km/h in a 120km/h Zone on the M1 in Lusk, Co Dublin.
In Co Louth, a motorist was detected travelling at 132km/h in a 120km/h Zone on the M1 at Dunmahon, Dundalk, with another travelling at 132km/h in a 120km/h Zone on the M7 at Ladytown, Naas in Co Kildare.
On the N71 Ballinvrinsig in Waterfall, Cork a driver was detected travelling at 146km/h in a 100km/h Zone.
Gardaí are appealing to motorists to slow down and drive safely.
The Road Safety Authority said that nine people were killed and 30 seriously injured in the last week of December last year alone
A spokesperson said excessive speed is a major contributory factor in fatal traffic collisions - and the higher the speed, the greater the likelihood of a collision causing serious injury or fatality.
Operation Slow Down is due to continue until 7am tomorrow.
Motorists in these areas were driving above the speed limit this morning:— An Garda Síochána (@GardaTraffic) December 23, 2022
88km/h in a 50km/h Zone on the Coolock Lane, Dublin 17
135km/h in a 80km/h Zone on the N4 Ballydowd, Lucan, Dublin 22
77km/h in a 50km/h Zone on the Limerick Road, Mallow, Cork. #SaferRoads https://t.co/gKdD9bMPZK
In December, 427 people have been caught driving under the influence of alcohol or drugs, Paula Hillman, Assistant Commissioner for Roads Policing and Community Engagement, has said.
Speaking on RTÉ's News at One, Ms Hillman said: "58 of those 427 were detected the morning after ... so the next day ensure that you have left yourself enough time before you get behind the wheel."
She said Go Safe vans will be in 162 locations across the country over the Christmas period, where she said the focus will be on the highest-risk areas for speeding.