The A815 is approximately 40 miles long and forms a connection between the A83 trunk road and the eastern part of the Cowal district; however it carries very little through traffic to and from central belt of Scotland as the Clyde ferries carry the bulk of traffic across the river, cutting journey times substantially, making commuting from the Clyde Coastal resorts a reality recognised by many.
Cairndow - Toward
This road commences at its northern end at the Dunoon Road End T-junction with the A83 in Glen Kinglas, close to the village of Cairndow. Heading south it almost immediately crosses Kinglas Water and bends sharply to the west following the course of the nearby A83 for a short while before running south westwards through forestry land, past a junction with the single-track B839 Hell's Glen Road and skirting the eastern shores of Loch Fyne. It passes through the villages of St Catherines and Creggans before meeting the A886 at a junction in Strachur. Here the A815 turns to head south east through Strachur. It crosses the River Cur and follows its course past the villages of Glenbranter and Invernoaden to reach Loch Eck, whose eastern shore is followed. At the southern end of Lock Eck it continues south following the course of the River Eachaig, past Benmore Botanic Gardens, before meeting the A880 at Ardbeg, more often referred to as Kilmun Turn.
Continuing south it crosses the River Eachaig and then the Little Eachaig River, before entering the long and fairly strung out settlement of Sandbank on the western shores of the Holy Loch. In the centre of Sandbank it turns off to the east towards Ardnadam, again following the western shores of the Holy Loch, the A885 continuing on from here to form a direct route to Dunoon.
Continuing east at first and then south again it continues through Ardnadam, rounding Lazzaretto Point before entering Hunter's Quay where small ferries make fast and frequent crossings to McInroy's Point on the south bank of the River Clyde close to Gourock. From here it passes through Kirn, and then into Dunoon. In Dunoon town centre it meets the other end of the A885 before passing Dunoon Ferry Terminal where passenger ferries make frequent crossings to Gourock, and passes close to the remains of Dunoon Castle.
It continues south along the western shores of the Firth of Clyde through Bullwood, Innellan, and Newton Park, passing its first junction for the village of Toward, and itself ending at a second junction for the village less than half a mile further. The road continues west from this point but is unclassified. Although this is the original 1922 ending of the road (actually the first junction for Toward was the 1922 end of the road), it was soon extended west of here to end on the shoreline at Port Lamont. It must have been cut back in the 1970s although it is not clear why.