Visual field restriction caused by motor cycle helmets.

The British Standard Classification for Productive Helmets for vehicle users (BS 6658: 1985) gives (para 5.5) requirements for "unobstructed vision". The parameters given are assessed by means of vertical and horizontal angles made with reference to two horizontal and one vertical reference planes.Restriction of lateral field was not found to be a problem unless wearing goggles. A full face /integral helmet caused a 38% reduction in vertical field and this was increased to 60% when wearing a jet helmet with sun shield and ventilation mask attachments.