Smart Motorway gantry sign
A gantry structure spanning the motorway with electronic signals, blue signs showing an exit and the following text.
Exit destinations: A412 Maple Cross.
Forward destinations: (M40, M4), Oxford; Heathrow [Airport symbol] Gatwick [Airport symbol] M25 .
Junction number: 17.
This is one of the quietest junctions on the whole M25, thanks to the fact it sits in the middle of protected green belt. There's only so many people who can live and work within reach of it.