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: M5 The SOUTH WEST [Solid diamond diversion symbol]; Bristol (W) & [Airport symbol]; The MIDLANDS; Gloucester (A38) Thornbury, Filton.
Right-hand two lanes destinations: SOUTH WALES; Chepstow (M48) M4 .
Junction number: 20.
Three lanes widen to four, and will shortly widen to five, as we approach our meeting with the M5. When we reach the junction three lanes will exit to the M5 and only two continue ahead.