DDA Guidance Part 5: This post covers the impact of the DDA on street furniture design.
Many guidelines advocate the use of colour / tonally contrasting marking to identify street furniture, although it may not be considered appropriate to use such treatments in historic areas. The main purpose of using contrasted marking is to help partially sighted people avoid obstacles that they might otherwise walk into or trip over.
Any free-standing post or column within an access route should incorporate a band that contrasts in colour and luminance with the remainder of the item. The band should be a minimum depth of 150mm, placed with the lower edge of the band between 1400mm and 1600mm above ground level. Some guidelines advocate deeper bands (300mm) or more than one band (three dark, two light bands each 100mm deep), but the single band, minimum 150mm, is acceptable to the Royal National Institute for the Blind.
Although colour contrasted bands on poles and colour contrast to the tops of bollards will help to some extent, the choice of colour for the overall post or bollard also affects visibility. Grey poles in particular are often problematic as they tend to blend into a paved background. The incorporation of a light at the top of bollards is an effective way of making them more easily seen.
It is essential to ensure that the colours used contrast with their surroundings; colours which appear to be different from one another in colour can be very similar tonally (eg green and brown) and therefore do not give sufficient contrast – particularly to individuals with colour blindness. Contrast is the difference in reflectivity between two surfaces. An easy way of judging whether there is good contrast is to take a black and white photograph of the scene or a photocopy of a colour photograph. A good contrast will show up black and white, poor contrast will show up as grey.
BOLLARDS
Generally, the use of bollards should be avoided as they clutter the streetscape and can create an unnecessary hazard for people with mobility and visual impairments. Improved legibility for both pedestrians and vehicle users through good design will minimise the need for bollards.
Bollards are recommended to be at least 1000mm in height. The same minimum height (1000mm) applies to other freestanding objects such as raised flowerbeds, which should also be designed with rounded edges. Under no circumstances should adjacent bollards be linked with chain or rope as this is a hazard for blind and partially sighted people.
Bollards can be customised for DDA compliance through the addition of contrast colours or finishes and reflective banding to break up the bollard outline and increase visibility as described above.
CYCLE STANDS
In order to assure DDA compliance, cycle stands can be customised through the addition of contrasting colours and/or reflective banding as described above.
The addition of tapping bars to Sheffield type cycle stands can also aid the visually impaired so that an empty stand can be identified by someone using a cane. Tapping rails are often added only to the two end stands in a run for reasons of economy.
Widths between stands should be a minimum 1000mm and ideally 1200mm.
LITTER BINS
Waste bins should be between 1000mm and 1300mm in height, should continue down or close to ground level and be of a rounded design in a colour that contrasts with their surroundings.
The bin opening should be approx 1000mm above ground level.
TREE GRILLES
If feasible, grilles should be positioned beyond the boundaries of any major pedestrian access route. Gratings within an access route should be of a non-slip finish and set flush with the surrounding surface.
Slots in gratings should be not more than 13mm wide and set at right angles to the dominant line of travel; the diameter of circular holes in gratings should be not more than 18mm (Heelsure drainage grates from Marshalls have slots of 6mm max for this reason). This recommendation is intended to reduce the risk of trapping the ends of canes and of wheelchair wheels becoming stuck.
GUARDRAIL
If there is a steep slope or drop at the rear of the footway, precautions must be made to prevent wheelchair users running over the edge or blind / partially sighted people walking over it. Guardrails and barriers at the side of or across footways should be at least 1100mm high; preferably 1200mm measured from ground level.
In common with other street furniture on or close by footways, guardrails should be clearly colour contrasted from their surroundings. If, for reasons of economy, galvanised railing is used, it should at minimum have colour contrasted markings added.
Guardrails should also be designed to prevent guide dogs from walking under the rails, but there must be sufficient openings between vertical elements to ensure that children and wheelchair users can see, and be seen, through the railings. The top rail should have a smooth profile and, if intended to provide support, should be circular with a diameter of between 40mm and 50mm.
There should also be an upstand a minimum of 150mm in height at the rear of the paved area, which can then act as a tapping rail for long cane users as well as a safeguard for wheelchair users.
Where it is necessary to provide staggered barriers across footways and footpaths in order to prevent conflict with other forms of traffic (for example at junctions with main roads) the barriers should be constructed of vertical bar sections 1200mm high and colour contrasted with their surroundings. An offset between the two barriers of 1200mm allows wheelchair users convenient passage but discourages the riding of bicycles.
CANOPIES
In order to provide shelter for those having to pause before entering a building other than a dwelling, the principal entrance should incorporate a form of weather protection, such as a canopy or recessed entrance, unless freely accessible automatic doors are installed.
Any part of the structure of a canopy should not present an obstruction to visually impaired people and contrast banding should be added to vertical elements.
SHELTERS
Shelters should be provided where there is space to do so. In locations not exposed to severe weather, a cantilever bus shelter with one end panel offers good accessibility and some weather protection. Where the end panel is used for advertising, it should be at the downstream end of the shelter so that people can see the bus approaching. In more exposed locations enclosed shelters should be provided if possible.
For reasons of personal security, the bus shelter should be made mainly of transparent material and well lit at night, though use of other materials may be more appropriate in rural areas. Where glass or transparent walls are used they should have a tonally contrasting band at least 150mm wide at a height of 1400mm to 1600mm from the ground. A second, lower band may be placed at 900mm to 1000mm above ground level.
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.