Since the introduction in the 1970s of green lettering on white background text signs indicating EXIT, Emergency Exit and similar directions, exit sign legends in the UK have changed format several times to make them more easily understandable by anyone, including non-English speakers.
The substitution of words by pictograms, the reversal of colours with white characters on a green background also serve to make the signs more easily recognisable from a greater viewing distance.
The original text only signs were superseded in 1990 with the introduction of UK standard BS 5499. This incorporated pictograms and text in a format which is still acceptable today as it meets the requirements of the 1995 European Signs Directive.
This Directive included a legend format without text, which was introduced into the UK in 1995 as the standard legend style to be supplied with new emergency lighting products.
From 2012 new BS ISO 7010 format pictogram signs will become legally acceptable and it is expected to become the preferred format to meet the requirements of the Signs Directive.
Certain organisations employ additional explanatory symbols or text in their signs. Such an example includes UK hospitals which generally require the use of signs in the Hospital Technical Memorandum (HTM) format.