Motorway gantry sign
A gantry spanning the motorway with blue overhead signs indicating one lane exiting and two continuing ahead, and the following text.
Left lane destinations: A4042; [Hollow square diversion symbol] Casnewydd; Newport; Cwmbrân .
Right-hand two lanes destinations: Caerdydd; Cardiff M4 .
Junction number: 25A.
This junction was added in the 1990s to connect to a new relief road north of Newport, and was designed to prevent traffic joining the motorway westbound at junction 25. Instead it helpfully gets some traffic off the M4 before the bottleneck just ahead.