Motorway fork sign
A blue sign with a diagram showing a branch off the road ahead and the following text.
Forward destinations: The WEST; (M25); Heathrow [Airport symbol]; (Terminals 2,; 3 & 5) .
Exit destinations: Heathrow [Airport symbol]; (Terminal 4; & Cargo) ; Hayes; Feltham; A312 [Hollow diamond diversion symbol].
Junction number: 3.
Heathrow is so large, and has so many terminals on different sides, that you need to approach it by different roads depending on where you're going. Your first decision is here at junction 3. Are you, by any chance, cargo?