350 drivers have been caught speeding so far on National Slow Down Day.
The 24-hour Garda operation will run until midnight.
Among the vehicles caught speeding is a motorist who was detected travelling at 134 kilometres per hour in a 100 zone on the N4 in Mullingar, County Westmeath.
A motorist was detected 113km/h in a 100km/h Zone on the N15 at Drumnagahan between Barnesmore and Donegal Town.
