The route starts at a T junction on the A5 a short distance west of Castletown and heads north along New Road, more commonly known as the Ballakeighan Straight. This extends for about half a mile before kinking right and crossing the steam railway line on a bridge next to Ballabeg Station. Heading north once more, the route becomes windier as it approaches Ballabeg village, ending at a TOTSO on the A7 at the southern entrance to the village.
As originally numbered in the 1920's, the route was given the B22 number. It had been renumbered as the A28 by 1963.