3.—(1) In a case where a journey is made by a vehicle (“vehicle A”) and an attendant employed to accompany A travels in another vehicle (“vehicle B”), the attendant is to be treated as employed in accordance with this Schedule only if—
(a)arrangements are made with a view to ensuring that, as far as is reasonably practicable, the attendant can see vehicle A at all times during the journey; and
(b)a direct radio voice link is in operation at all times between vehicle A and vehicle B.
(2) In all other cases, the attendant is to be treated as employed in accordance with this Schedule only if effective arrangements are made to ensure that the attendant is in a position to observe the vehicles and any load and give any necessary warning.