UK Road Vehicle Lighting Regulations 1989 paragraphs 19 and 24 refer to the visibility of vehicle lights. It is an offence for the structure of the body or any devices used in conjunction with the body to obscure the visibility of any obligatory lights. For full details and clarification please refer to the above regulations. Specifically, paragraph 19 refers to the constructors responsibilities (vehicle body-builder for example) and paragraph 24 refers to the vehicle driver's / operator's responsibilities