The regulation refers to motor vehicles:

Prohibition against vehicles overtaking at crossings24.—

(1) Whilst any motor vehicle (in this regulation called “the approaching vehicle”) or any part of it is within the limits of a controlled area and is proceeding towards the crossing, the driver of the vehicle shall not cause it or any part of it—

(a)to pass ahead of the foremost part of any other motor vehicle proceeding in the same direction;

or(b)to pass ahead of the foremost part of a vehicle which is stationary for the purpose of complying with regulation 23, 25 or 26.(2)