DDA GUIDANCE PART 4: THIS POST COVERS THE IMPACT OF THE DDA ON SIGNAGE DESIGN, MAINLY FOR THE VISUALLY IMPAIRED.
People need information about the purpose and layout of spaces if they are to maintain a clear sense of direction and independent use of a building. Signs should form part of an integrated communication scheme that gives clear directions, information and instructions for the use of a building. They should support a wayfinding strategy that considers the needs of different types of users as well as the complexity of the area’s layout. The orientation of maps and plans should match that of the building.
The effectiveness of information on the use of a building is determined by:
a) the location, accessibility, layout and height of signs
b) the size of lettering, symbols and their reading distances
c) the use of tactile letters and symbols
d) colour/luminance contrast and lighting
e) the finished surfaces of materials used for signs and symbols
f) the simultaneous use of audible cues
g) integration with any other communication systems.
All key information, such as sign directories, orientation signs, maps and plans, should be visual and audible, and in tactile form where low enough to be touched. As no single medium can communicate information to all those who need to receive it, some duplication will be necessary. Information may take the form of visual (eg signs), audible (eg public address systems and infrared devices), or tactile (eg signs with embossed lettering or Braille).
The height above ground of any controls for signage that need to be operated from a wheelchair should be at least 750mm and not more than 1200mm above ground level. For non-wheelchair users, the height of controls may be between 1000mm and 1400mm. Clear signs and information are essential for people with impaired hearing who may be unable to ask, or feel uncomfortable about asking, for directions.
Symbols are an essential aid for people with learning difficulties and universally recognised pictograms should be used to replace text, wherever possible. Other symbols should supplement text, but should not be used in isolation.
Directional signs should be placed only on fixed parts of the building such as walls, posts and floors. Consideration must be given to duplicating detailed signs or instructions, especially safety notices, at high and low level, ie at 1400 to 1700mm for a visually impaired person when standing and 1000mm to 1100mm for close viewing by a wheelchair user. Signs should be in a matt finish and positioned to avoid reflections from daylight and artificial lighting.
Finger posts in areas of high pedestrian flow should carry a visibility band as described above.
Low level signs supported on two vertical poles (eg city maps) should have a lower tapping rail or skirting between the posts to prevent blind pedestrians inadvertently walking between them and colliding with the sign. The rail or skirting should be 300-400mm above ground level; the sign must not extend more than 150mm beyond the supporting posts.
Overhead signs (and any other obstacles over a footway) should give the height clearances of 2100mm min below suspended signs, 2300mm otherwise.
Background: originally partly prepared through my role as a member of the technical comittee of the the Landscape Institute and partly as Woodhouse continue to consult with clients, charities and landscape architects on the subject of the DDA.