The A3110 is one of three roads in the Scilly Isles. It forms a loop on St Mary's, meeting the A3111 and A3112, which link to the population centres on the west of the island, in the southwest corner. The islands had no classified roads until the 1960s when the three A-roads were created by being cobbled together from unclassified roads. As befits its history - and the lack of traffic on the island - the road is narrow and poorly signed.
Starting from the southwest corner of the A3110 (where it TOTSOs on meeting the A3111) the road heads northeastwards along Telegraph Road. It bears left at a farm entrance to pass another couple of farm buildings before it TOTSOs right onto Town Lane. The road winds eastwards via the hamlet of Maypole before turning southwards to avoid getting too close to the east coast. After passing the farms at Normandy the road turns sharply right and heads westwards once more along Carn Friars Lane. After the A3112 turns off to the left the road soon returns to the TOTSO it started at.