 The section from the Capel Llanilltern Interchange on the M4 ( junction 33 ) to the Queen 's Gate roundabout is sometimes referred to as the Western Link Road ( Welsh : Ffordd Gyswllt <unk> ) , is 15 @.@ 77 kilometers ( 9 @.@ 80 mi ) in length and includes the Capel Llanilltern – Culverhouse Cross Link Road , Ely Link Road , Grangetown Link Road and Butetown Link Road . For the majority of this section it is the boundary between the City of Cardiff to the east and the Vale of Glamorgan to the west . 
