Smart Motorway gantry sign
A gantry structure spanning the motorway with electronic signals, blue signs showing the left lane exiting and three others continuing ahead, and the following text.
Exit destinations: A13 ; Tilbury; Thurrock; Lakeside; L'dn (E & C).
Forward destinations: (M20, M23), Dartford Crossing; Gatwick [Airport symbol] M25 .
Junction number: 30/31.
This one sliproad serves both junctions 30 and 31, which is why both numbers appear here on the signs. If the A13 isn't for you (and I don't know why it wouldn't be, it's perfectly nice) then we are about to cross the river.