Indeed, much of the route comprises roads that were formerly part of the N7 between the cities, prior to motorway and other bypasses.

The official description of the R445 from the Roads Act 1993 (Classification of Regional Roads) Order 2012 [1] reads: Between its junction with N7 at Maudlings in the county of Kildare and its junction with N80 at Stradbally Road in the town of Portlaoise in the county of Laois via Dublin Road, Poplar Square, Main Street and Limerick Road in the town of Naas: Newhall, Buckleys Cross: Liffey Bridge, Main Street and Edward Street in the town of Droichead Nua; and Ballymany Cross; Dublin Street and Claregate Street in the town of Kildare; Cherryville Cross, Mayfield (including link road to M7); Mooreabbey and Dublin Street in the town of Monasterevin; and Clogheen in the county of Kildare: Kilinure, Ballybrittas, Cappakeel, New Inn Cross, Greatheath, Ballydavis; Rathbrennan and Dublin Road in the town of Portlaoise in the county of Laois and between its junction with N80 at Abbeyleix Road in the town of Portlaoise and its junction with N62 at Benamore in the county of North Tipperary via Grattan Street in the town of Portlaoise; Clonboyne, Cloncourse; Portlaoise Road, Main Street, Market Square, Bridge Street and Patrick Street at Mountrath; Holy Cross, Moorefield Cross, Rush Hall, Derrin Cross, Borris-in-Ossory and Ballaghmore Lower in the county of Laois: and Cooleeshill in the county of Offaly and between its junction with the N62 at Parkmore in the county of North Tipperary and its junction with N52 at Tullahedy via Inane in the county of North Tipperary Ouris and Busherstown in the county of Offaly: Greenhills in the county of North Tipperary: Moneygall in the county of Offaly: Toomevara, Clashnevin, Lisbunny: Dublin Road, Thomas MacDonagh Street, Pearse Street, Kickham Street, Ashe Road and Clare Street in the town of Nenagh: and Springfort Cross in the county of North Tipperary and between its junction with N52 at Lissenhall in the county of North Tipperary and its junction with the N18 at Cratloemoyle in the county of Clare via Ballinteenoe, Kilmastulla, Gortybrigane and Birdhill in the county of North Tipperary: Dalys Cross, Mountshannon, Annacotty and Groody Bridge in the county of Limerick: Parkway Roundabout, Dublin Road, Clare Street, Lock Quay, Abbey River Bridge, Northern Relief Road, Castle Street, Thomond Bridge, High Road, Sexton Street North, Northern Ring Road, Ennis Road, Caherdavin Cross and Ennis Road in the city of Limerick: Lansdowne Bridge at the boundary between the city of Limerick and the County of Clare: and Meelick in the county of Clare.

South of Naas, the R445 becomes a dual carriageway for 8 km (5.0 mi) and crosses the M7 motorway at Junction 10, continuing west to Newbridge along the town's Dublin Road, crossing the River Liffey via Liffey Bridge onto Main Street.

The route continues along Edward Street, leaving the town as the Kildare Road.

From the Carrigatogher Roundabout the R445 leaves the N52 road and continues along the old N7 route to Birdhill which was redesignated in April 2010.

Finally, the route through Limerick city, which formed the N7 prior to the opening of the Southern Ring Road in 2004, is also now the R445.

The route passes by Annacotty, and enters Limerick along the Dublin Road through Castletroy.