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: A4810; [Hollow diamond diversion symbol] [Hollow circle diversion symbol] Magor; Magwyr; Caldicot .
Right-hand two lanes destinations: Caerdydd; Cardiff Casnewydd; Newport M4 .
Junction number: 23A.
For some reason there are only two lanes under the roundabout at Magor, so the five lanes of motorway that crossed the Severn now merge into two to cross junction 23A.