Speed limits could go as low as 30 kilometres per hour on the M50, under new variable limits.
Changing speed limits will be brought in on some sections of the motorway in the next few weeks.
It will start between Junction 4 Ballymun and Junction 6 Castleknock in the next few weeks and will roll-out across the entire M50 by 2023.
Speed limits will change depending on road conditions and incidents and will be shown on screens above the motorway.
But Transport Minister Eamon Ryan says at the start it won't be legally enforceable:
"It's starting on an advisory basis which is right, an appropriate test to make sure the whole system works but myself and Minister Naughton are introducing legislation, or due to introduce legislation in the Dail this term, which will put it into statute, into law, be fully legal."
