Are touch screens accessible?
A touch screen is a computer display screen that is sensitive to human touch, allowing a user to interact with the computer by touching pictures or words on the screen.
Touch screens today are frequently used for information kiosks, automated teller machines (ATMs), airline e-ticket terminals, and customer self-service stations in retail stores, libraries, and fast food restaurants. Touch screens are also the most common means of input into personal digital assistants (PDAs).
Since touch screens were designed to provide user-friendly, intuitive computer access without requiring a keyboard and mouse, it logically follows that touch screens can be excellent tools for people who experience difficulty using keyboards and mice because of physical or cognitive disabilities. In fact, touch screens have been used as assistive technology for many years, providing an alternative to standard input devices for users who need access to standard applications. Specially designed applications have also been developed specifically for touch screen use. These applications typically include large icons and a simple intuitive design layout.
Despite advantages to some, however, touch screens can present barriers to others, such as people with physical disabilities who are unable to touch the device, as well as people with low vision and blindness, for whom the device provides no controls that can be appreciated by sense of touch.
For people who are physically unable to touch the device, an accessible product is one that allows the individual to enter commands by voice or by pressing the controls with a mouthstick, headstick, or other similar device (stylus). Some touch screens support stylus input, and others do not. The difference is in the device's touch sensor technology, of which there are several common types:
- Resistive touch screens are pressure sensitive, so they can be operated with any input device, including a gloved hand or stylus. However, resistive screens can be easily damaged by sharp objects, and they offer only 75% clarity, which may create additional problems for people with low vision.
- Capacitive touch screens offer higher clarity and are more durable, but they do not respond to gloved hands or most styluses (the pointing device must be grounded).
- Infrared touch screens can be operated by either human touch or stylus. They also provide high clarity and durability. They are more receptive, however, to false responses (by dirt, flying insects, etc.) and do not respond well to users whose fingers hover before pressing a control.
- Surface acoustic wave (SAW) is a more advanced technology that provides high clarity and durability and can be operated by either human touch or stylus. This technology, however, is considerably more expensive than the more common technologies and is not as well supported.
People who are blind and some people with low vision are unable to locate the controls of a touch screen device. These individuals may be able to locate and activate controls if they are labeled in a large high-contrast font and/or if audible output is provided to help identify the controls. Audible output is also required for users with visual impairments to access the information that results from activating the controls. An interesting field in computing is haptics, which is the science of applying tactile sensation to human interaction with computers. This has the promise of providing a method for accessing touch screen information in an alternative format, such as through audio or tactile sensation. Lund University in Sweden published a paper entitled User-Centered Design of Non-Visual Audio-Haptics in 2008. The Trace R&D Center has conducted extensive research into designing touch screens that are accessible to people with visual impairments. For more information, consult the Trace publication Use of audio-haptic interface techniques to allow non visual access to touchscreen appliances.