Dublin city's first static speed camera has come into operation on the Crumlin Road in Dophin's Barn.
Anyone found to be driving in excess of the limit will be issued with a fixed charge notice, which carries three penalty points and includes a €160 fine.
A static speed camera differs from an average speed camera system as it is only measures a motorist's speed at one particular point along the road.
Dolphin's Barn was identified as part of national analysis as a road that could benefit from a safety camera, gardaí said.
They said this location was selected based on the number of fatal and serious crashes there over the last seven years, speed data and feedback from stakeholders.
In March, static speed camera came into operation in Co Limerick and Co Meath.
