The B511 forms the pre-bypass A2 through the County Down coastal village of Groomsport. The number seems to have come into existence in 1962 when the A-road moved to a new bypass of Groomsport .
The road starts at a roundabout at the eastern end of the A2 Bangor bypass and follows Bangor Road through a wood into the open fields. There is a glimpse of the sea on the left then the road enters Groomsport and becomes residential.
We now follow Main Street above the harbour. A road leads off left to the pier, after which the B511 becomes lined with buildings again. After another couple of glimpses of the sea the road heads south, back inland, and soon ends at a T-junction back on the A2.