A blue sign with a diagram showing a branch off the road ahead and the following text.
Forward destinations: London; Cas-gwent; Chepstow.
Exit destinations: ; High Cross; B4591.
Junction number: 27.
This is a local exit for the Newport suburbs, one of several junctions that make this bit of motorway very heavily used and prone to delays. But it gets worse in a minute where the road gets narrower.