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Figure 10.5. Open space way-finding
avoid reducing its width. However, the posts could still interfere with the canes of long cane users.
•Temporary signs of interest to vehicle drivers and cyclists, such as the presence of diversions, should be located at the side of the road and not on the pavement.
•As far as possible, street furniture should have appropriate dimensions to make it more obvious without blocking the path. In practice, the size of most street furniture is determined by its applications.
•The avoidance of potential hazards that can easily snare long canes, such as litterbins supported on a column. The use of a larger bin that sits on the pavement is preferable.
•Consultation with disabled people, including blind and visually impaired people.
Visually impaired and blind people may find open spaces, such as shopping precincts, pedestrian areas and small parks, particularly inaccessible due to the lack of landmarks for way-finding and the hazards posed by the often seemingly random arrangement of street furniture. The provision of well-defined paths marked by tactile paving or other surfaces and high contrast colour strips can make wayfinding much easier. Trees and bushes add to the attractiveness of open spaces, but they need to be carefully sited so that they do not obstruct pathways (see Figure 10.5).
10.3 Physical Environments: Buildings
Many buildings were constructed before there was any awareness of the importance of accessibility. Public buildings are now being modified to improve accessibility, but modifications at a later date are not always as successful as designing in accessibility from the start. Building regulations (for public buildings) in most countries now cover accessibility. There is recognition of the need for a percentage of the housing stock to be wheelchair accessible, but there seems to be less awareness of the need for all housing to be as accessible as possible to give disabled people the
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widest possible choice of where to live and enable them to visit other people freely. Some of the main accessibility principles in the building regulations are discussed in this section.
10.3.1 General Exterior Issues
Access to buildings from the street involves an approachway and an entrance to the building. Buildings may also have external stairways, for instance to allow emergency exit from the building.
Approachways
The approach to the main and preferably all entrances to a building should be wide enough for a wheelchair or two people to walk abreast. The main and preferably all entrances should have an approach which is free of steps, with a ramp with slope of less than 1 in 20 used to overcome any difference in height between the entrance and the road and any gradient. In practice, this may mean that the main entrance has both a series of steps leading directly up to it and a ramp along the front or side of the building that may zigzag to give sufficient length to cover the increase in height without an excessive slope. High-contrast colour edging strips, tactile surfaces and handrails, on both steps and ramps, should all be used to lead pedestrians to the building entrance safely.
Entrances
The entrance to a building should be clearly identifiable and free of obstructions. If the entrance has a canopy, its supporting columns should be designed and sited to avoid creating a hazard. Lighting can also be used to make the entrance distinctive and accessible at night, but it should be diffuse and/or shaded to avoid causing problems to people with light-sensitivity or visual processing impairments. Automatic sliding doors are accessible to most people, but space considerations or other factors may make their installation physically impossible. Indeed, where space considerations permit, a choice of entrance should be provided. Tactile tiling should be used to alert people to the door and lead them to it. Some of the issues to be considered in entrance design include the following:
•The door width should be at least 1.2 m to enable a blind person with a sighted guide or guide dog or a wheelchair user to enter easily. Pillars or other obstacles should not be allowed to compromise this width requirement.
•Revolving doors should be avoided if possible.
•Thresholds to the doorway should be flush with the floor.
•Tactile flooring on both sides should be used to identify the location of doorways.
•Glazed or plate-glass doors should use patterns and high contrast signs to indicate the location of the door.
•Door furniture should be sensibly positioned, be of simple design and have a high contrast colour.
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•Spring-loaded doors should have a carefully regulated spring-pressure to enable them to open easily and to prevent them springing back and injuring someone passing through slowly.
Exterior stairways
These stairways are generally provided as an emergency exit (or entrance) rather than for regular use. Therefore, their construction tends to be basic but robust. Despite their infrequent use, it is important that they are as accessible as possible to all members of the community, though they unfortunately cannot be made accessible to wheelchair users. Features that can be used to increase their accessibility include the following:
•Tactile warning surfaces to indicate the start and end of the stair well.
•A clear indication of the edge of the stairs. This should preferably have both tactile and visual indicators, such as a high contrast, tactile edging strip.
•A high contrast coloured handrail on each side of the stairway.
•Adequate illumination of the stairway after dark.
•Appropriate design at ground level to avoid causing a hazard to pedestrians. This should include high contrast signage and a suitable railing or fence around it, if required. The location may make it unnecessary to fence off the stairway.
Signage
All public buildings should have signage in large high contrast lettering, as well as tactile signage. The numbers of private houses should also be larger and clearer than at present. A standard location for displaying them would also be helpful.
10.3.2 General Interior Issues
There are a number of general points that can be considered in order to create an accessible interior environment.
Logical layout
Public (and private) buildings should have a logical layout that facilitates navigation and finding the main facilities. This includes a logical room numbering system, for instance with one number indicating the floor or level and a second number the particular room on the floor. Consecutive numbers should be used for adjoining rooms and the number system should avoid missing out numbers or jumping from high to low numbers and then back to high numbers. Good layout design requires consideration of both people working in the building and people visiting it to access goods and services. In older buildings, it will be possible to modify the existing layout to a certain, though sometimes limited extent in order to improve accessibility. However, even where the layout is less than optimum, lighting, signage and d´ecor can be used to improve accessibility and make the building more attractive and pleasanter to use.
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Spatial dimensions for easy passage
A key objective in public buildings is to achieve good circulation areas with dimensions that allow easy passage for all. Where possible, all passages, doors, stairs and lifts should be 1.2 m wide. The following list indicates the minimum passage width to allow passage of particular groups of people:
•Person with walking stick 750 mm.
•Person with a guide dog 1100 mm.
•Person with a sighted escort 1200 mm.
•Person using two crutches 900 mm.
•Wheelchair user 900–1000 mm.
Hazard-free passage
This has two components: the building structure, which cannot be modified without structural changes and moveable furniture and obstacles. Structural obstacles include support columns, fixed door widths, steps, and stairways. The dimensions and structural requirements of the building, as well as cost considerations, may make it impossible to change these features. However, the use of good colour contrasts, panelling, tactile paving and appropriate lighting can draw attention to these features and minimise their hazard potential. If appropriately designed, these features can also serve as orientation points. Moveable obstacles include both semi-permanent features, such as seating, (low) tables, drinking water fountains, fire extinguishers and sand buckets and temporary obstacles left by building users. All these features need to be appropriately located away from passageways so that they avoid causing a hazard and can easily be located and used by both blind and visually impaired people and wheelchair users. All building users should be careful not to leave equipment, clothing or anything else where it can cause an obstacle. Accessibility also requires the maintenance of the building in a good state of repair to avoid, for instance, the need to use buckets to catch drips. Particular care is required when repairs take place inside a building that is in use to reduce potential hazards, for instance, due to the presence of builders’ ladders, and to inform building users of the need for particular care.
Lighting and d´ecor
Lighting and d´ecor, including the use of good colour contrasts, can make buildings more accessible to blind and visually impaired people. Tactile floor and wall markings and surfaces are also important for improving orientation and ensuring a safe passage round the building for blind people. There seems to be an increasing tendency to use very bright direct lighting in the entrances and passageways of some public buildings. This use of direct lighting should be avoided, as it makes them inaccessible to people who are light-sensitive or have some visual processing impairments. Lighting and d´ecor also have an important role in contributing to the attractiveness and welcoming atmosphere of public buildings. This should
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be considered an important component of accessibility rather than a competing or conflicting requirement, since public buildings are intended to be used and a building that feels unwelcoming and unattractive may turn away some potential users. Lighting and d´ecor are discussed in more detail in Section 10.3.3.
Signs
Finding a route through a building is often a matter of following signs. Therefore, a well-designed signage system that provides information in a variety of formats and has a logical structure is required. Otherwise, all users, especially blind and visually impaired people, are likely to get lost and have a frustrating time trying to reach their destinations. Signage is particularly important in large buildings and complexes of buildings, such as university campuses. Signage can be divided into two main categories: directional and locational. Both types are equally important, since users require signage both to find the lecture hall they are looking for and to identify it so they know they have reached the correct location. All signs should be appropriately located to make them perceptible and should not be obscured. Where possible, combination of tactile signs, large high contrast lettering, symbol signs, picture or icon signs and audio signs (to be received over a headphone of standard design) should be used.
Building services
Building services is the usual term given to all the additional service items needed to run a building; items like power systems, water supply and lifts come in this category. Often these services are the responsibility of a building services engineer. Two factors need to be considered concerning the accessibility of some building services, such as security door systems, lifts, escalators and moving pavements (travelators): all building users, including blind and visually impaired people, should be able to locate and use them easily and potential hazards should be avoided. This requires the use of signage, tactile paving and appropriate location.
Special purpose rooms
Many of the rooms in public buildings serve a designated purpose, such as a canteen or a dining room, office, hotel bedroom, interview room or toilet. In addition to general accessibility considerations, particular attention should be given to ensuring that all functions of these rooms are fully accessible. It can be seen that the list of accessibility guidelines easily becomes extensive when special purpose rooms are considered and, for this reason, no further discussion of these special purpose room issues is given in this chapter.
Soundproofing
Unfortunately, accessibility guidelines, such as those resulting from the Americans with Disabilities Act (ADAAG 2002) generally do not consider the issue of soundproofing. However, it is covered in many building codes. Appropriate
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soundproofing both between rooms and on external walls and windows to cut out external sounds is important for both disabled and non-disabled people. As well as reducing stress and physical and psychological illness from external traffic and other sounds and the potential for disputes between neighbours, a quiet environment makes it easier for hearing impaired people to hear signals of interest, such as conversations and visually impaired people to perceive relevant auditory environmental cues.
The weighted sound reduction index gives a measure of the extent to which, for instance a wall, insulates sound by attenuating sound travel through it. It is determined over a frequency range of 100 Hz to 3.15 kHz (NI, undated; AZBUILD, undated), which covers the main speech frequencies, but does not cover the higher frequencies perceived by the human ear. Typical values in building codes are 55 dB for internal walls.
10.3.3 Lighting and D´ecor
Lighting
Good lighting is very important for illuminating the interior of a building, particularly at night. It can also be used to improve accessibility by indicating or drawing attention to the location of particular facilities. Lighting and d´ecor also contribute to the ambience and attractiveness of a building. General points to be considered in designing the lighting system include the following:
•Dramatic changes of lighting levels from one public area to the next should be avoided. Uniformly distributed lighting facilitates the passage of visually impaired and blind people around the building. People with certain types of visual impairments may adapt slowly to changes in light levels and this can create a hazard if lighting levels change suddenly.
•Glare can be caused by light reflection from polished surfaces such as floor coverings, windows, computer screens and furniture. This can lead to temporary blindness for people moving through these areas and therefore care should be taken to avoid possible sources of glare.
•Lights should be adequately shaded. Very bright lights with little shading can cause problems for people who are light-sensitive or have certain types of visual processing impairments and should therefore be avoided. Unfortunately, this type of lighting seems to be used increasingly in entrance halls, access corridors and lifts.
•As far as possible, lighting systems should be designed to avoid shadows or dark areas caused by objects in the path of an illuminated source, as they can obscure pathways and create visual illusions, leading to confusion and possible accidents. This is particularly important in public access areas and should be checked at different times of day and night.
•Different types of lighting, including overhead lighting and task lighting, should be provided to enable users to choose the best type or combination of lighting
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Table 10.1. CIBSE recommended lighting parameters |
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Location |
Task/function |
Maintained |
Limiting |
Minimum colour |
|
|
|
illuminance |
glare rate |
rendering (Ra ) |
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|
|
(lux) |
(UGR) |
|
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|
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Entrances |
Halls, lobbies, |
200 |
22 |
80 |
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waiting areas |
|
|
|
|
Enquiry desks |
Face-to-face |
300 |
22 |
80 |
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transactions |
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|
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Airport: escalators |
Local pedestrian |
150 |
22 |
80 |
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and travelators |
movement |
|
|
|
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Kitchens |
Food preparation |
500 |
22 |
80 |
|
Offices |
General clerical |
500 |
19 |
80 |
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work |
|
|
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Public car |
Parking areas |
75 |
– |
20 |
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parks (indoor) |
|
|
|
|
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Railway stations |
Covered platforms |
50 |
28 |
40 |
|
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Open platforms |
10 |
– |
– |
|
|
Waiting rooms |
200 |
22 |
80 |
|
Theatres, |
Foyers |
200 |
– |
– |
|
Concert halls |
Auditoria |
100 |
– |
– |
|
|
Toilets |
200 |
25 |
80 |
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to meet their needs. Many visually impaired people can find task lighting, which focuses on the task being performed, very useful, whereas some light-sensitive people and people with visual processing impairments may not be able to use task lighting.
•The ability to adjust the level of lighting, particularly in special purpose rooms, such as offices, is very useful to enable all building users to have appropriate levels of lighting. This would be very useful in hotel bedrooms, where the lighting is often very dim.
•Building regulations and guidelines generally include recommended lighting levels for specific building areas. They should be consulted and provide a useful indication. However, the recommended lighting levels do not always provide sufficient illumination to meet the needs of visually impaired people. A typical set of guidelines for recommended lighting values is that produced by the U.K. Chartered Institution of Building Services Engineers (CIBSE), a section of which is shown in Table 10.1 (CIBSE 2002).
Illuminance
The science and measurement of lighting is a well-developed aspect of building services engineering. To present detailed information about this field is beyond the scope of this book but it is very useful to understand the main technical parameters involved. Definitions of the full range of parameters used in lighting
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can be found in a joint publication of the Commission Internationale de l’Eclairage and International Electrotechnical Commission (CIE 1987). The first parameter is illuminance. This quantifies the amount of luminous light flux received at a surface and is usually measured in lumens per square metre or lux. Thus, the lighting levels in a room or interior can be correlated to the supplied illuminance.
Units for light
The measurement units for light are based on the solid spherical geometry of a point source radiating light uniformly outwards to illuminate a concentric spherical surface, as shown in Figure 10.6. The sphere enclosed by this surface has a solid angle of, 4π steraradians (st).
The light source emits radiation. This gives a radiant flux across the sphere, which is the radiation energy transported per unit time and therefore measured in watts. This energy flux produces luminous flux on the surface, which is measured in lumens. The luminous intensity is the luminous flux per unit solid angle and this is measured in candela, with one candela equal to one lumen per steradium. Alternatively, a candela can be defined as the luminous intensity in a particular direction of a single frequency light source of 540×10−12 Hz with a power of 18.3988 mW energy intensity in that direction of 1/683 W/sr. The total flux in lumens can then be obtained from the luminous intensity in candela by multiplying it by the solid angle in steradians into which the light is emitted. The illumination or brightness is the surface density of the luminous flux received. It is measured in lux with one lux equal to one lumen per square metre.
Most lighting designs are described in terms of illuminance quantities, namely the amount of luminous flux (lumens) per unit area reaching the various surfaces in an environment. However, the visual system also responds to qualitative factors such as glare and colour in determining whether the lighting promotes visual comfort and visual satisfaction. These two issues provide the next two parameters for discussion; the limiting glare rating and the index of minimum colour rendering.
Figure 10.6. Units for light measurement
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Glare
Glare results when there are bright and dark areas in the field of view or some areas in an environment that are much brighter than the general level of brightness. Glare can be divided into the following three categories:
•Blinding glare, for instance from staring at the sun. This results in temporary total loss of vision and leads to temporary visual impairment. It is generally not relevant in indoor environments.
•Disability glare, which is the presence of excessive illumination that reduces vision to the extent that objects and details can no longer be seen. It could be caused by oncoming car lights.
•Discomfort glare, which results when an interior experiences a much higher level of illumination than is necessary for its role. Although not dangerous in itself, it is very irritating and can lead to fatigue if experienced over an extended period. A common cause is prolonged exposure to an over-illuminated interior, which results in a general feeling of discomfort from being in the area; hence the name of discomfort glare.
Units for glare
Based on experimental research, discomfort glare has been shown to be dependent on the luminance and size of the source of illumination, as well as its position in the field of view and the general level of luminance in the (interior) environment. These factors have been combined into a formula from which the degree of discomfort glare can be computed as a unified glare rating (UGR). Thus for a given illuminated interior, it is possible to compute its UGR value and compare this with a recommended limiting UGR value. If the recommended limiting UGR value is exceeded, then the lighting system should be redesigned. In general disability glare will not be a problem if discomfort glare is maintained within appropriate limits. In addition to other sources of glare, many modern appliances, such as mobile phones and MP3 players, are backlit and the resulting glare can be very distressing to people who are light-sensitive. Limiting glare rating values for disability and discomfort glare for a variety of appliances are given in CIBSE (2002).
Colour
An important feature of surface colour is its reflectance. Colour systems are used to describe and specify the effects of a particular colour scheme. In the Mansell colour system, three quantities are used to specify colour: value, chroma and hue. Colour value relates to its lightness and hence to its reflectance. Colour chroma defines colour strength and colour hue specifies the type of colour, for instance whether it is red, yellow, green, blue or purple. These terms can be used to specify and describe the appearance of the coloured surfaces of a room.
The following two physical properties: (i) the apparent colour of the emitted light and (ii) the colour rendering are used to quantify the colour properties of light. These properties are defined by the Commission Internationale de l’Eclairage
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(CIE) (CIE 1995). In specifying the properties of interior lighting systems, it is the index of colour rendering that is generally most important.
Units for colour rendering
Colour rendering is the ability of a light source to render or replicate the colours of surfaces. The CIE general colour-rendering index is a measure of the accuracy with which a light source or lamp is able to reproduce a set of test colours when compared to the test colour reproduction of an appropriate standard light source. The colour rendering index, Ra ranges from 0 to 100, with 100 signifying perfect agreement in colour rendering. Only the highest values indicate good colour performance, with a colour rendering index of less than 80 signifying that a lamp should not be used in areas where people are working for extended periods.
The Code for lighting document (CIBSE 2002) provides lighting specifications for a very wide range of interior and exterior light systems. The general reader might be surprised to find lighting specifications for locations as diverse as bakeries, autopsy rooms, steel rolling mills and cold stores. The specifications are given in terms of
(i) the illuminance in lux, (ii) the limiting glare rate on the UGR scale and (iii) the minimum colour-rendering index, Ra. Table 10.1 shows typical recommended lighting specifications.
D´ecor
D´ecor is very important. It both contributes to the attractiveness and ambiance of a building, room or facility and provides clues to support way-finding and safe passage. These two functions should be seen as complementary rather than in competition, though compromises will sometimes have to be made. However, it needs to be recognised that accessible buildings should also be attractive ones. Strong colour contrasts are required to assist visually impaired and blind people in differentiating building features, such as walls from floors, and locating doors, door handles and light switches. These colour contrasts should be chosen to be harmonious and attractive, for instance by using a very dark shade of a particular colour against a very pale shade of the same colour.
Figure 10.7 illustrates how poor d´ecor selection could lead to confusion and a potential accident point in a public library. The carpet flooring and the built-in textile-covered reading seat between two fixed bookcases are an identical carmine red shade and of a similar texture. As a result, visually impaired people could miss seeing the seat due to the lack of colour contrast and try to reach to the open space beyond through the ‘gap’ between the bookcases, leading to minor accidents.
Mirrors and glass panels are sometimes used to give the impression of more space. Since visually impaired people can find this very disorientating and may try to walk through the apparent open vista in front of them, the use of mirrors and panels in this way should be avoided.
Some simple principles for the interior decoration of public buildings are given below (Barker et al. 1995):
• Wall finishes should be matt and use pale tones.