Motorway gantry sign
A gantry spanning the motorway with blue overhead signs indicating one lane exiting and the other lane continuing ahead, and the following text.
Left lane destinations: M4e ; London; Bristol (C); (M32) [Solid triangle diversion symbol].
Right lane destinations: M4w ; SOUTH WALES; Chepstow; (M48) [Hollow square diversion symbol].
Change Route: M4 London or M4 SOUTH WALES
The lanes divide - left for London and the east, right for Wales and the west.