New slower speed limits will come into effect in the city centre from midnight tonight.
New 30 kilometres per hour speed limits will come into effect around areas like Dolphins Barn, Kilmainham and Smithfield.
The AA have criticised the move but Councillors backed it in December with Dublin City Council saying it will save lives.
Currently, the 30km/h zones operate in the core city centre area and in the suburb of Marino.
The measure is also set to be extended to residential zones like Sandymount, Drimnagh Crumlin, Glasnevin and Cabra at the end of May.