|From:||Kylemore Road, Chapelizod (W) (O097347)|
|To:||Frank Sherwin Bridge, Dublin (O139344)|
|Distance:||4.4 km (2.7 miles)|
|Meets:||R112, R111, R101, R148|
|Former Number(s):||N4 T3|
The R109 begins at a junction with the R112 Kylemore Road to the west of the Dublin suburb of Chapelizod. After running southeastward along Lucan Road for some 570 m, the route swings left and then right, crossing the Anna Livia Bridge in Chapelizod to reach the north side of the Liffey. From here the R109 continues eastward along Chapelizod Road and Conyngham Road with Phoenix Park to the north and the river to the south. Soon after meeting the R111 – coming in from the right in the district of Islandbridge – the route terminates opposite Dublin Heuston railway station at a junction with the R148 (former N4) at the northern end of the Frank Sherwin Bridge.
The R109 from Chapelizod towards the city was the main approach to Dublin from the West, being the T3 in the original 1920s numbering scheme and later the N4. While the straight Conyngham Road was a reasonable route for motoring, the bridge at Chapelizod was a bottleneck and this became a major problem as national traffic increased and Dublin suburban development spread into areas beyond Chapelizod. The redirection in 1987 of the N4 on to the good quality D2 Chapelizod bypass (now R148), on the south bank of the Liffey, alleviated the traffic problems and meant that the now R109 ceased to form part of the strategic road network.