The Road Vehicles (Construction and Use) Regulations 1986

30.—(1)  Every motor vehicle shall be so designed and constructed that the driver thereof while controlling the vehicle can at all times have a full view of the road and traffic ahead of the motor vehicle.

(2)  Instead of complying with the requirement of paragraph (1) a vehicle may comply with Community Directive 77/649, 81/643 or, in the case of an agricultural motor vehicle, 79/1073.

(3)  All glass or other transparent material fitted to a motor vehicle shall be maintained in such condition that it does not obscure the vision of the driver while the vehicle is being driven on a road.