LRV is a universal value for 'contrast'. It measures the proportion of useful light reflected by a coloured object. It represents a relative light and darkness value rather than an actual colour. Therefore, dissimilar colours could have the same LRV.
LRV is measured on a scale of 0 to 100, 0 being perfect absorbing black and 100 being perfect reflecting white (in reality you never find these perfect objects - a bright white would typically have a result of an LRV of 85).
The current guidance in the Regulations and in Codes of Practice, BS 8300:2009, is that adequate visual contrast is provided if the Luminous Reflectance Factor - Light Reflectance Values (LRV) of the contrasting areas differ by at least 30 points. The current British Standard for the measurement of LRV is BS8493:2008+A1:2010.
Obligations regarding building access and usage are covered under BS8300 / Building Regulations Approved Document. Failure to comply with the Equality Act could result in building owners and facility managers being fined up to £50,000.
The regulations mean that people, regardless of disability, age or gender, must be able to gain equal access to public buildings. For visually impaired people this means amongst other things that there must be a good visual contrast between various elements of the building, including doorways, fixtures and fittings. Therefore, the contrast between for example doors and walls must achieve a certain level – measured by something called Light Reflectance Value (LRV).
Most registered blind people will still have some vision in colour. Only a small percentage (less than 5%) can see nothing at all, and even people within this group will generally have some sensitivity to light and shade. Ensuring that a minimum of 30 points of LRV difference is specified for adjacent surfaces will in the majority of cases help to ensure that visually impaired people are not discriminated against.
Examples where visual contrast will be required: