4.—(1) Subject to the following paragraphs of this regulation, a vehicle shall be smoke-free if it is used —
(a)for the transport of members of the public or a section of the public (whether or not for reward or hire); or
(b)for work purposes by more than one person (even if the persons who use it for such purposes do so at different times, or only intermittently).
(2) This regulation applies to vehicles and parts of vehicles which are enclosed.
(3) A vehicle or part of a vehicle is enclosed for the purposes of paragraph (2) where it has doors or windows which may be opened but it is not enclosed unless it is wholly or partly covered by a roof.
(4) This regulation applies to all vehicles other than —
(a)aircraft;
(b)ships or hovercraft in respect of which regulations could be made under section 85 of the Merchant Shipping Act 1995 (c. 21) (safety and health on ships), including that section as applied by any Order in Council under section 1(1)(h) of the Hovercraft Act 1968 (c. 59) or to persons on any such ship or hovercraft; or
(c)private vehicles.
(5) In this regulation “roof” does not include any roof which is completely stowed away so that it does not cover any part of a compartment in which persons may travel.