The now dismantled bridge over the River Bandon near Kilnacloona, upstream of Kinsale
The L42 was a long route along the south coast of County Cork. It started 6 km south of Bantry, on the T65 at Keilnascarta, from where it headed south 12 km to Ballyhedob before turning left to run eastward through Skibbereen and Clonakilty to Kinsale. Here the River Bandon was originally crossed by a 1.5-km-long, narrow 19th-century bridge, some way upstream of today's R600 crossing, which was completed in the later part of the 1970s.
Beyond Kinsale, the road turned northwards to reach Cork City, running through Riverstick and past Cork Airport. The terminus of the L42 appears to have been on Merchant's Quay in the city centre, close to the junction of the T6 and the T29, although the exact location remains to be confirmed.