This article is about the Class III road numbered C78 maintained by DfI Roads. For other roads numbered C78, see C78.
The C78 is the only C road on the Islandmagee Peninsula. It starts on the B150 at the north end of Islandmagee village and crosses the peninsula heading east. The road then follows the east coast of the peninsula northwards with a view out into the North Channel where, on a clear day one can see across to Galloway in Scotland. The road encounters a couple of 90 degree bends as it moves slightly inland and soon after, the road re-joins the B150. Mullaghboy is just over the hill from here.