Interacting with Terminals
On most terminals, the visual instructions on the screen are the main guide for the user. There are a large number of factors that determine whether reading the screen will be difficult or easy for disabled or elderly persons.
People who wear bifocals find it difficult to read the screen of most public access terminals since the screen may not be at a suitable distance for the near or far segments of their spectacles. In addition, many people leave their spectacles in the car or do not wear them in public. The number of people who have problems in reading the screen is much more than the 1.5% of the population considered to be blind or to have low vision
the most common forms of colour blindness are inherited and are associated with the inability to discriminate red and green wavelengths. Because these defects are inherited as recessive traits, the incidences are much higher in males (C. 8.0%), who possess a single x-chromosome, than in females (C. 0.5%), who possess 2. Total colour blindness is rare (C. 0.0025%).
Sunlight can degrade the ability to view a display for all users. The screen should be shielded from direct or reflected sunlight or other bright light sources. The display should be viewable from the eye level of a person sitting in a wheelchair. People with low vision should not be prevented from getting their faces close to the screen.
The conflicting requirements of tall pedestrian users and short wheelchair users can lead to a significant group of users having parallax problems when lining up the function keys with the displayed option. Lines on the user-interface leading from the key to the surface of the display can alleviate this problem.
Developments in wireless interfaces make it feasible for a disabled user to have a hand control unit with a remote link to the terminal. This would require all terminals to use the same interface protocol and care would be needed to ensure confidentiality of sensitive information.
With the deployment of near-field communication (NFC) technology in mobile phones, the opportunity for a wireless link between the terminal and a user's handset is fast becoming a cost-effective option.NFC enables a user to exchange all kinds of information simply by bringing two devices close together.
Keypads and controls
Controls should say what they do and do what they say. This is reinforced if they are intuitive to use and easy to remember. There needs to be consistency both within and across applications. Additionally, controls should be compatible with how people expect them to move, e.g. Up is up and left is left. Any display associated with the controls should be aligned appropriately. Using concepts that are familiar to the users will enable people to accurately guess at how a function will operate. This should correspond to their expectations, e.g. The direction of reading is a powerful transferable stereotype.
A standard layout for keypads is essential for blind people. There are currently two common layouts for numeric keys; the telephone layout and the calculator layout. It is recommended that the telephone layout be used exclusively on public access terminals.
Enlarged raised keys enable persons with poor dexterity to press the correct key; a concave shape to the keys will also help fingers to stay in place. However, some disabled people prefer convex keys since they can be activated by the hand for those unable to use their fingers. The spacing between the keys is as important as the size of the keys. When a person has difficulty making precise finger movements, large keys that are recessed or guarded can help to ensure that the wrong key is not pressed. For many disabled people it is important to be able to connect an external keyboard to suit their specific needs.
The standards in various countries differ over the embossed symbols to be used on the function keys. A typical example is shown in the picture below.
Ideally keys should be internally illuminated when the terminal is waiting for input from that keypad. Auditory feedback in the form of sounds such as a â€œbeepâ€ or â€œclickâ€ when a key is pressed is helpful to many people and enhances feedback and, subsequently, performance.
Many older people and those with a cognitive impairment do not like to be rushed or to think that they are likely to be â€œtimed outâ€ by the machine, so it is necessary to allow for such people to use the terminal at their own pace; this requirement could be stored on the user's smart card.
As keypads are often used in a secure context, they often need to be hidden from the view of others. This can be achieved by the addition of a privacy shield. Since the principle purpose of a privacy shield is to block the keys from view, this can pose serious problems with respect to accessibility, both visually and physically.
In general, it is recommended that the user ensures maximum privacy by positioning his/her hands and body so that they shield the keypad and/or screen. However, the required actions cannot always be achieved with ease. Poor manual dexterity, for example, can limit the number of simultaneous actions that can be carried out using both hands. Likewise, the ability of a customer to shield the keypad and screen with his/her body will depend on the height at which the keypad and screen are located. A person of small stature or a person in a wheelchair may not be sufficiently high to block the keypad and screen from the view of other people. Although privacy shields should serve to alleviate these problems, there have been difficulties in implementing privacy shields without reducing accessibility.
The sides of the privacy shield can be angled inwards to give more room around the keypad, but this increases the total area taken up by the keypad. A possible alternative is to have a removable (e.g. Hinged) privacy shield for people who have problems in using the keypad when the shield is in place. However, this may be difficult to make vandal resistant and it may be difficult to discourage users from removing the shield.
Touchscreens are considered useful in situations where inputs are limited and well defined. However, on a single screen controls can be reconfigured. This can render them difficult to use for visually impaired people who are not given a chance to learn where the controls lie and their association. It is important to ensure that labels are not made to look like controls. Problems with parallax can also limit the effectiveness of touchscreens.
Whilst being used, the finger and hand can obscure what is on the screen. Smudges left by fingers on the screen can decrease legibility. Touchscreens can be very difficult for blind people to use because it is difficult to locate the control/active area and know whether this has been activated. However, it is possible to design the system so that there is spoken output when the finger is over an item on the screen but activation is only when the finger is withdrawn over an active area. With this arrangement there should be only a small number of well-spaced active areas.
It can be tiring to hold your arm up for a long time and pointing is not very accurate, people tend to hit below the target. Accuracy is best for targets nearer the bottom of the screen. This is thought to be due to the position of the arm and parallax problems. The vertical size of the target affected the error rates. To decrease the errors made by activating the wrong button, large touch-sensitive areas or soft buttons with a minimum of 20mm height and width are recommended.
It is possible to increase the size of the characters on the screen for individual customers who require this facility. This can be done by selecting this option from a menu or, preferably, by storing this information on the customer's smart card. For example, it could be arranged that holding your finger in the bottom right corner for at least 2 seconds indicates that you would like larger characters on the screen.
The following are key accessibility considerations:
- All controls and touchscreens should be reachable from a wheelchair;
- The screen should be shielded from sunlight;
- Allowances should be made for red/green and blue/yellow colour blindness;
- An inductive loop facility and jack socket should be provided;
- Provide an easy-to-use interface with the ability to increase character size, text accompanied by graphics and optional speech output;
- There should be tactual differentiation of keys with appropriate colour coding;
- The telephone layout for numeric keys, with a raised dot on number 5, should be used;
- Extra time should be allowed for important input;
- If possible, provide a keyboard alternative to the touchscreen;
- On touchscreens, ensure active areas are well separated.
More detailed information is provided in the guideline on displays.