Smart Motorway gantry sign
A gantry structure spanning the motorway with electronic signals, blue signs showing the left two lanes exiting and the other two continuing ahead, and the following text.
Left-hand two lanes destinations: SOUTH WALES ; Chepstow (M48) M4 w London M4e.
Right-hand two lanes destinations: The MIDLANDS; Gloucester M5 .
Junction number: 15.
Change Route: M4 SOUTH WALES & London
We pass over the roundabout at junction 16 and immediately reach the exit for junction 15. If you exit here you’ll merge with traffic from the A38 for a short but very lively bit of road where everyone is changing lanes all at once.