Restrictions on the nature of lamps fitted on or to a vehicle
22.—(1)  No vehicle shall, subject to these Rules, show —
(a)a red light to the front; or
(b)any light to the rear, other than a red light or a white light for the purpose of reversing.
(2)  Paragraph (1) shall not prevent a vehicle from carrying a lamp showing a light to the rear for the purposes of —
(a)internal illumination of the vehicle;
(b)illuminating an identification mark, a taxi meter, or any device for giving signals to overtaking traffic; or
(c)in the case of a public service vehicle, illuminating boards, plates or devices indicating the route or destination of the vehicle.