Gatwick 
Smart Motorway gantry sign
A gantry structure spanning the motorway with electronic signals, blue signs showing a "tiger tail lane drop" where the left lane exits, the right hand two lanes continue ahead and the second lane from the left can go in either direction, and the following text.
Exit destinations: (A23) [Hollow diamond diversion symbol] Gatwick [Airport symbol].
Forward destinations: Brighton, Crawley M23.
Junction number: 9.
Change Route: M23 Gatwick Spur
Lots of traffic departs here for Gatwick Airport, but also for the fairly substantial towns and industrial parks that surround it. If you're exiting here use the left hand lane - you can use either lane to turn right towards the airport but nobody reads the signs so you can get past a whole line of cars that way.