Design principles
In this section we give general advice on what should be taken into account to make products more easily used by older people and people with disabilities - so that they are easier to use by as many people as possible.
- Seven Principles of Design for All : from The Center for Universal Design
(see Contacts - Other Useful Web sites) - Practical Product Principles : an overview of the points raised by RICA's work which need to be considered for mainstream products to be more easily accessible
- Human Factor Categories : information on the implications of impairments.
For checklists for 10 mainstream products go to
Product Group Checklists
Seven principles of design for all
The Center for Universal Design at North Carolina State University in USA (see Contacts - Other Useful Web sites) has developed the following broad principles.
- Equitable use: the design must be useful and marketable to any group of users - avoiding segregation or stigmatisation of any users.
- Flexible in use: the design must accommodate a wide range of individual preferences and abilities.
- Simple and intuitive use: the design must be easy to use and understand, regardless of the user's experience, knowledge, skills or concentration level.
- Perceivable information: the design must communicate necessary information effectively to the user, regardless of ambient conditions or the user's sensory abilities.
- Tolerance for error: the design must minimise hazards and the adverse consequences of accidental or unintended actions.
- Low physical effort: the design must be usable efficiently and comfortably and with minimum fatigue.
- Size and space for approach and use: appropriate size and space must be provided for approach, reach, manipulation and use, regardless of the user's body size, posture, or mobility.
Practical product principles
Controls
- easy to reach: without the need to bend or stretch
- large enough to grip easily: small fiddly controls put strain on the joints used in bending fingers and hands
- non-slippery surface: the greater the friction of the surface, the less force is needed to retain the grip
- protruding or raised rather than recessed: easier to locate by touch, and open space around a protruding control allows it to be operated by swollen and inflexible fingers, or the side of a very weak or painful hand; recessed controls provide limited space for fingers only, requiring a specific grip
- requiring light pressure to operate: this decreases the pressure required from the user's fingers
- avoid controls requiring dual action, such as push and twist: they require continued pressure and twisting at the wrist, painful or impossible for some people
- well spaced rather than cramped or close together: provide enough space around each control for swollen fingers or a hand with tremor
- use some different shapes and sizes: so different controls can be identified by touch
- large clear labelling: use strong colours that contrast against the background colour
- tactile markings: need to be easy to locate and feel, to guide partially sighted and blind people
- provide essential information in different modes: pictorial, tactile, lights and sounds
Stability
- must not tip over easily
- effective anti-slip bases: particularly helpful for one-handed use
Accessories
- easy action to connect and disconnect: without the need for precision or strength
- avoid fiddly parts: awkward to set up
- separate storage as an alternative: to reduce the weight of a portable product
- cleaning
- avoid unnecessary markings: they trap dust and debris and make cleaning difficult
- avoid sharp edges: uncomfortable or even painful to touch or grip
Portability
- no heavier than necessary to lift
- good holding places or carrying handle: well placed, comfortable, space for two hands
- good balance and shape: so that it does not strain joints, nor swing into the person carrying it
Instructions
- clear, straightforward layout
- clear, straightforward type face
- large type size: 14 point where possible, not below 10 point, and good space between the lines
- strong colour print on a light background
- matt paper or with a slight sheen: glossy paper reflects light and is more to difficult to read from
- offer alternative formats: large print (14 point minimum), Braille and audio tape
Human factor categories
- mobility
- balance
- muscle strength
- dexterity
- vision
- hearing
- cognition
Brief information follows on the broad categories of impairment that should be taken into account in product design. The design for all approach necessarily addresses this range of needs. In older age people are more likely to have multiple impairments - for example some hearing, sight and physical strength loss are all typical.
Mobility
Difficulty in walking can be caused by foot, leg, hip or back problems. Many people can walk only a short distance and many rely on a walking aid such as a stick. Speed of movement is also affected. Bending over or down to reach or pick up something will be difficult, so the height of any task will be important. Adjustable heights are helpful to people with walking difficulties. They are likely to choose to sit at a task which others will carry out standing.
The height of any object or task will be particularly important to people who cannot walk at all and use a wheelchair. Reaching low will be difficult and can unbalance their position. Items above a certain height will be unreachable. Some wheelchair users have other disabilities, for example in their upper body which will further restrict their reach.
Whether people are unable to walk or walk with difficulty, they are likely to have problems bending, reaching, lifting and turning.
Balance
Difficulty in maintaining equilibrium can have a physical cause eg lack of strength in the lower body, and a sensory cause eg difficulty in processing visual information. Older people are more likely to experience dizziness. Firm and safe supports should be provided where hands will easily find them, and the need for stretching should be avoided. In designing products and layouts, attention should be paid to preventing trip hazards.
Dexterity
Arthritis is a common cause of poor dexterity, creating pain in the joints and limited movement and weakness in the arms and hands. In handling products people cannot get a firm grip, have limited strength to pull or push, and they find precise finger movements impossible or painful. Actions that require force or a tight hold put pressure on the fingers and strain on the joints. The discomfort and pain are prolonged if continued force is needed. Double actions, such as push and twist, are particularly difficult for people with poor dexterity. The use of one hand and arm can be more restricted than the other, so people may use just their stronger hand to carry out tasks. Those with paralysis on one side will do everything one handed.
Vision
There is a continuum of visual impairment. Short- and long-sightedness are very common and both usually corrected by spectacles. There are a number of more severe impairments which prevent people seeing images clearly and fully. They include a reduced field of vision, including tunnel vision, difficulty in perceiving depth, in distinguishing similar colours from each other, difficulty focusing and seeing an interrupted image, such as spots before the eyes. At the extreme is blindness. Some blind people can distinguish light and shape, others have no awareness of light. People who are blind depend on tactile information on products. Few use braille but all will use raised markings and shapes to feel their way round an item.
The ability to discriminate detail and to discriminate differences between levels of contrast both decline with age. Older people need more light to distinguish objects than younger people. Difficulty reading small print is common after the age of around 50.
People who use visual information, whatever their level of impairment, are helped by large print and good colour contrast, and matt paper or surfaces: avoid reflecting surfaces and dazzle. In handling products people with poor sight have difficulty with visual displays, seeing markings and labelling and any assembly that involves small parts. Printed instructions are a problem. Information should be as short and simple as possible, the layout straightforward, and as well as large print and strong colour contrast, sans-serif typefaces are generally easier to see.
Hearing
People of any age can be hearing impaired but loss of hearing is part of the natural ageing process. The high frequencies or tones are usually lost first. People with a moderate hearing impairment, who are hard of hearing, have difficulty hearing conversation and specific auditory information, particularly against background noise. People with severe impairment, deaf people, cannot use hearing for communication.
Product design should use a combination of audible with other signals, such as visual. Any audible elements should be adjustable where possible, so that both volume and tone can be adjusted to suit the user.
Cognition
Cognitive impairment affects the ability to take in information and attend to it, to learn new things, to make decisions and to solve problems. The ability to concentrate declines in older age, so older people have difficulty keeping their attention focused on a task. The increased use of medication can cause drowsiness.
People with cognitive impairment are helped by simple displays and the use of obvious sequences and patterns. Information is more difficult to remember if it has no clear structure. Printed text should be kept to a minimum, with steps and choices clearly illustrated graphically. People should not be expected to remember complex operations.
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