Little symbols on road signs

[HogF]

Usually circle or diamond shape in a small yellow box. What are they for?

[sddsddean]

They are temporary diversion signs and are used for motorway and major road diversions. They are normally used due to the emergency closure of a motorway or road section. If a section is closed, there are usually fold up signs at the junction you are directed off at, which the Police will unfold, saying 'For M1 North follow O' or whatever the symbol is. As the diversions signs are already up and ready, there is no more for anyone to do, except hope that none of the signs have been knocked down!!

[paulz]

Down here in Sussex they're a permanent fixture. It shows a diamond as the alternative route to Heathrow using the "A" roads [instead of the M25 car park], and I think coming back its a circle for Gatwick