(1) A traffic-related item of a kind mentioned in these Rules has effect for these Rules if--(a) the item is on a road, or on a vehicle on a road, and(b) the item complies substantially with these Rules.
(2) A traffic-related item is taken to comply with these Rules unless the contrary is proved.
Note 1 :
"Road" includes a road related area--see rule 11(2).
Note 2 : Rule 322(1) and (2) explain the meaning of a traffic control device on a road.