The B198 follows the original route of the A2 through Holywood in County Down.
The road starts at traffic lights at the eastern end of the A2 bypass and heads southwest along the residential Bangor Road. We zigzag past the remains of Holywood Priory and then reach the High Street. There's a straight run past the shops then the road bends to the left to pass the modern St Colmcille's Church and then become residential. We leave town along Belfast Road, after which the road returns to the A2, with traffic having to continue west towards Belfast; A2 traffic may join the B198 from either direction,