Motorway fork sign
A blue sign with a diagram showing a branch off the road ahead and the following text.
Forward destinations: Caerdydd; Cardiff; Abertawe (G & Dn); Swansea (N & E); Castell-nedd; Neath.
Exit destinations: Llangyfelach; B4489; Felindre; [Hospital (with A&E) symbol].
Junction number: 46.
The need for bilingual directions in both Welsh and English mean that you can expect road signs on the M4 to be skyscrapingly tall, like this one, through to the Severn estuary.