The new Sallins bypass in north Kildare will open today.
The road marks the completion of a €110 million project and is the second phase of the overall project to be delivered.
This has funded the widening to three lanes in each direction of the M7 between Naas and Newbridge and the addition of an interchange off the N7 on to the Naas ring road.
Fianna Fail TD for North Kildare James Lawless said: "I am delighted to see these infrastructural improvements become reality having campaigned for them for over twenty years.
This investment in local road infrastructure will provide immediate relief to my own village of Sallins which has been beset by traffic for decades.
It will also greatly improve motorway access and traffic flows for residents all around Naas, Clane, Straffan, Prosperous and beyond."