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INTERACTIVE SYSTEM DESIGN & EVALUATION
Accesibility (DISABLED USERS,…
INTERACTIVE SYSTEM DESIGN & EVALUATION
- Accesibility
ADDRESSING ACCESSIBILITY
- One size doesnt fit all because humans are diverse.
- The Equality Act 2010
- Types of disability
- Website accessibility and the Equality Act 2010:Discrimination against people with disabilities is prohibited by law, but website owners often don't realise how the law affects websites.(Taylor A.)
https://seqlegal.com/blog/website-accessibility-and-equality-act-2010
- What range of users are able to use the system?
- Does a particular physical or mental disability make task impossible or is this an interface problem?
- How can we enable as many users to use the system?
- Accesibility for disabled users
- Normal users are quite diverse
PHYSICAL CAPABILITIES
- Humans vary in many dimensions:
- Size of hands may affect the size and positioning of input buttons
- Motor abilities may affect the suitability of certain input and output devices
- Height - short or tall cant see fixed screens?
- Strength - a childs toy requires little strength to operate but greater strength to change batteries
- Disability (eight, hearing, dexterity etc.)
ERGONOMICS
- Human factors (origin in US military), Ergonomics is British term
- Ergonomics primarily concerned with fitting artefacts to abilities, limitations, performance characteristics of human minds
- DISABILITY DISCRIMINATION ACT 1995 (DDA): defined a disabled person as someone who has a physical or mental impairment that has a substantial and long-term adverse effect on his or her ability to carry out normal day-to-day activities
INTERNET AND THE LAW
- EQA - The Equality Act (2010) consolidated and superseded previous anti-discrimination legislation, including
- DDA - Disability Discrimination Act 1995 (Extended in 2005 to include private and company intranet sites). DDA aimed to ensure that disabled users have accessto the same information and content as able users have
- SENDA - Special Educational Needs and Disability Act 2001. SENDA established legal right of disabled student not to be discriminated against
- In 2006 Disability Rights Commission & British Standards Institute published guide to good practice for accessible sites
- used against companies in court
- W3C Web Content Accessibility Guidelines
- Basis of ruling in Australia (Sydney Olympic Games website wasn't accessible using refreshable braille display and web browser)
- Cases brought by RNIB in Britain havent come to court
EQUALITY ACT 2010
- EQA (and previously DDA) makes it unlawful to discriminate against disabled in the way in which you:
- recruit and employ
- provide services
- provide education
- Discrimination can take place in two ways
- by treating a disabled person less favourably
- by failing to make "reasonable adjustments" so that disabled people can participate in employment and education or make use of a service
DISABLED USERS
-
DISABLED IN UK
- Over 8million registered disabled users
- 2 million with sight problem; 360,000 registered blind or partially sighted
- 1 child in 1000 born with severe hearing loss
- 50,000 people in UK use British Sign Language as primary language
- 9 million have hearing loss -12 million 60+ and growing --21% of population
DISABLED IN USA
- Over 8 millio blind or visually impaired; of these 1.3 million legally blind
- 20 million deaf and hard of hearing people in the US about 1 million can't understand speech
- Over quarter million spinal cord injuries
- 0.5 million cerebral palsy
- 1/3 million multiple sclerosis
AGEING
- Physical impairment become more common with time
- More than 1/2 of 65+ have impairment
- This is a rapidly growing group, in 2000 were was 34.8 million people over 65 - projected to be 53.7 million by 2020
VISION
- PARTIAL SIGHTEDNESS
- low visual acuity
- tunnel vision
- central field loss
- clouded vision
- ASSISTIVE TECH FO PARTIALLY BLIND
- large monitors, choose large front displays
- screen magnifiers (zoom facility)
- Sound
- WEBPAGE BARRIERS FOR PARTIALLY SIGHTED
- Wheb pages with absolute font sizes that do not change size
- Web pages with inconsistent layout - difficult to navigate when enloarged due toss of surrounding content
- Web pages, or images on webpages, that have poor contrast, and wose contrast cannot be eaily changed through user override of author style sheets
- Text presented as images, which prevents rapping to the next line when enlarged
BLINDNESS
- ASSISTIVE TECH FOR BLIND
- Screen readers: text to speech synthesizer
- Refreshable braille display
- Text-based browsers, or voice browsers
Use rapid navigation strategies (e.g. tabbing through headings and links) rather than reading every word in sequence
- Discriptive audio
- SMARTPHONE CAMERA
KNFB: photo to speech synthesizer
- iPhone or Android app, or specialized reader
- Photographs text and reads it
- Developed by Ray Kurzweil and National Federation of the Blind
- WEBPAGE BARRIERS FOR BLIND (W3C)
- Images that do not have alternative text
- Complex images (e.g. graphs or charts) thatre not adequately described
- Video not dexcribed in text or audio
- HTML tables that do not makesense when read serially (in a cell-by-cell or "linearized" mode)
- HTML frames that do not have "NOFRAME" alternatives, or that do not have meaningful names
- Forms thant cant be tabbed through logical sequence/ poorly lableled
- Browsers and authoring tools that lack keyboard support for all commands
- Browsers and authoring tools that do not used standard APIs for the OS they are based in
- Non-standard document formats that screen reader has difficulty interpreting
COLOUR BLINDNESS
- 8% male population
- most common red/green indestinguishable (deuteranopia)
- BARRIERS
- Colour that is used as a unique marker to emphasize text on a web site
- Text that inadequately contrasts with background colout/patterns
- TOOLS
- Use own style sheets to override colour choices of author
- DESIGNING FOR COLOUR BLINDNESS
- Design principles: Strong brightness contrast
- But people with nornal vision need this too
- Different colours at similar luminance: very hard to read text or see detail
PHOTOSENSITIVE EPILEPSY
- Also called photo convulsions
- Can be triggered by rapidly flashing lights
- Danger range 3 to 60Hz
- Trigger frequencies vary
- 3 to 30Hz most common; worst at 20Hz
- Only a small minority affected but a serious issue for those who are susceptible
- DESIGN PRINCIPLE: avoid using flashing text
MOTOR IMPAIRMENT
- Include weakness of muscles, limitations of muscular control, joint problems, paralysis or missing limbs
- Can be caused by
- Disease: arthritis, muscular dystrophy, multiple sclerosis
- Stroke
- Injury
- Loss of limb
- RSI
- Ageing
- Wide range of assistive devices to utilise residual motor abilities
ASSISTIVE TECH FOR MOTOR IMPAIRED
- Maltron left-handed keyboard
- Sip and puff headset
- Without keyboard:
- by pointing
- by scanning and selecting
- Predictive typing
- Morse code
- BARIERS
- Time-limited response options on webpages
- Browsers and authoring tools that do not support keyboard alteratives for mouse commands
- Forms that cannot be tabbed through in a logical order
DEAFNESS
- Some deaf people have sign language as their first language, may not read a written language fluently
- Barriers include:
- Lack of captions or transcripts of audio on the web, including webcasts
- Lack of content-relatted images in pages full of text,
- Can slow comprehension for people whose first language may be a sign language instead of written/spoken language
- Lack of clear and simple language
POOR HEARING
- Complete deafness uncommon, but poor hearing widespread
- Can he helped by hearing aids
- Cused by prolonged exposer to noisy environments
- hearing degrades with age
- ASSISTIVE TECH FOR DEAF
- American - DePaul U
- British - TESSA (U of EA)
DYSLEXIA
- Difficulty processing written language and /or images
- May use several modalities (channels) to process information at the same time
- BARRIERS
- Lack of alternative modalities for information on websites, for instance lack of alternative text that can be converted to audio to supplement visuals, or the lack of captions for audio
