 The route starts in the townland of Aghaboe, County Laois, at a motorway-to-motorway interchange with the M7.From here it proceeds southwards, passing under the R434 and R433 roads until it runs parallel to the single-carriageway R639 road, bypassing Abbeyleix, Durrow, Cullahill, Johnstown, Urlingford, Littleton, Horse and Jockey, Cashel, New Inn, Cahir, Skeheenarinky, Kilbeheny, Mitchelstown, Kilworth Mountain, Fermoy, Rathcormac, Watergrasshill and Glanmire.Between its junction with the M7 and Dunkettle, the M8 passes through pasture in County Laois, and over bogland and coniferous forest through County Kilkenny and County Tipperary.