​​​​​​​​​​​Access protection markings, also known as H bar markings, are white lines placed on the road, normally in front of driveways and garages.
​​​​​​​​Marciau amddiffyn mynediad, sydd hefyd yn cael eu galw’n farciau bar H, yw llinellau gwyn ar y ffordd, fel arfer o flaen rhodfeydd a modurdai.