Users who are blind, partially sighted or colour blind should be able to perceive all of the outputs from the terminal. The outputs include any information that is presented and any physical items that are delivered, such as tickets, cash, receipts and returned cards.
Where possible, visually displayed information should be delivered in a form that users who have partial vision or colour blindness can see. Where this is not possible, or for users who are completely blind, an alternative form that they can perceive should be made available and should provide the same information.
Visually impaired users should also be able to notice when any delivered outputs have appeared and where. Preferably, they should be able to anticipate exactly when and where the delivered outputs will appear so that they can be ready to grasp them as soon as possible.
Information output is usually provided as text and presented visually. Any user who cannot see to read the text will not be able to perceive the information it contains. Not being able to see text well enough to read it is often due to a combination of poor vision, inadequate text quality and poor lighting. By increasing the legibility of the text or the lighting, even users with some visual impairment will be able to read and understand it.
Movement reduces legibility and some users who can read quite well are nevertheless unable to read the same text if it is moving.
Often the only way the user knows something has happened is by listening to incidental noises, such as the click of the counter in a ticketed queuing system, the sound of the printer in a ticket machine or the whir of the motor in a cash dispenser. Even users who are totally blind can gather information about the outputs by listening for these noises. Although these noises are incidental, similar sounds can be included intentionally, ranging from simple clicks and beeps to spoken alerts.
When information outputs are displayed visually as written text, non-sighted users will need to be able to hear it spoken, although care should be taken not to compromise the user's security.
Directions and Techniques
Ensure that characters are at least 4mm high. Light text on a dark background is best for contrast, e.g. White or yellow on black or a dark colour. Avoid using pale colours. Avoid red on green or yellow on blue. Avoid patterned backgrounds for text. Avoid all caps and underlining. Use a typeface that has numerals with open shapes such as Tiresias.
Supplement visual cues, such as flashing indicator lights, with simultaneous corresponding audible cues, such as clicks, beeps and spoken alerts.
Applying the previous techniques should result in a terminal that suits all users. However, in some cases, what is best for one group of users is not necessarily best for all. If this is the case, it may help if the user interface can be adapted by the user, or automatically for the user, to fit their individual capabilities. For example, users who are visually impaired could choose voice output and large type, whilst users with good vision may prefer to have more detail and no sound. The choice could be made by the user selecting from a number of displayed options. Alternatively, information required for the terminal to switch automatically could be encoded on a user's smart card at their request.
Whilst colour coding can be useful as an aid to recognition, it should not be relied on entirely since more than 8% of Irish males and some females have difficulty distinguishing between red and green (other forms of colour blindness are relatively uncommon).Ensure that rigid outputs such as cards protrude at least 2cm from the slot surround and that flexible outputs such as receipts protrude at least 3cm.
Ensure that the machine's grip on outputs such as money, tickets, receipts and returned cards is no more than is necessary to prevent them being pulled out by the wind or other environmental conditions.
If tickets are delivered using perforated paper rolls, make sure the perforations are easily broken by a tugging motion.
How you could check for this
Designers can run simple sight tests on an early prototype by simulating various types of vision loss. Complete loss of sight can be simulated by wearing a blindfold, turning off the lights or putting the terminal in a black bag. To simulate partial sight, a test user who normally wears glasses could take them off. It is also possible to buy low vision simulation glasses that simulate various types of visual impairments. In all cases, extreme care should be taken to avoid injury through loss of balance or collision with unseen objects. This may require that the test user remains seated or, if they have to move around, obstacles such as floor cabling are removed in advance. Although this type of ad hoc testing will not replace proper testing with real users, it will give some insight into what it is like to be operating with reduced vision.
During development, test the prototype in a realistic situation with real people who have various forms of visual impairment. Ideally, include people who are recently impaired and have not yet developed enhanced perception or coping methods. This is the only way to find out if the audio equivalents can be understood by users well enough to provide the intended information.During testing, the following key checks should be made:
- Ensure that documents protrude at least 3cm;
- Ensure that cards protrude at least 2cm;
- Make sure that minimum force is needed to withdraw a card.