Mobile interfaces for older adults need to be usable, engaging, easy to use, meaningful, and motivate the adoption of technology . However, current mobile technologies do not meet the needs, experiences, and limitations of older adults, and have many usability problems [16, 17]. A number of web design guidelines [18–21], design principles [22, 23], heuristics , and mobile and touch screen design guidelines and recommendations [12, 24] were developed to address the usability problems with interfaces for general population. However, current design guidelines and principles address focus on specific limitations and disabilities, mostly vision impairments, as well as cognitive and motor limitations. This approach fails to account for the entire range of limitations and combinations of limitations that characterize the diversity of the population of older adults.
Due to the gap between the current mobile design guidelines for user interface design and the needs of the diverse population of older adults, this paper describes a project to provide an overarching set of inclusive and complete UD guidelines for mobile interactive interfaces for older adults. The set of inclusive UD guidelines was developed integrating mobile design guidelines , UU principles , results of the usability studies with older adults , and DfA approach with UD principles and guidelines . It was also expected that the design of usable user interfaces for older adults would also enhances the usability for all other user groups and improves the users’ overall experience .
Voting interface EZ Ballot was designed using design criteria which were based on the set of integrated inclusive UD guidelines for UIs  with the addition of the UD guidelines applicable to the voting systems (6a, 7a, and 7b). Design criteria for the voting interface are measurable and performance-based criteria. Guidelines and criteria are listed below based on each UD principle (guidelines are numbered, and corresponding design criteria, DC, are listed below each guideline):
Principle 1: Equitable Use: The design is useful and marketable to people with diverse abilities.
1a. Provide the same means of use for all older adults: identical whenever possible, equivalent when not.
DC: Provide one type of voting system to all voters regardless of their abilities.
1b. Avoid segregating or stigmatizing any older adults.
DC: Avoid specialized voting systems for voters with disabilities.
1c. Provisions for privacy, security, and safety should be equally available to all older adults.
DC: Reduce the chance of older adults being vulnerable by providing several error-proof and privacy-proof mechanisms. Provide a touchscreen not visible to people standing next to the voting poll but the voter himself.
1d. Make the design appealing to all older adults.
DC: Seemingly integrate simultaneous visual and audio ballot interfaces. Use familiar design features. Avoid institutional appearance. Use a human voice as an audio sound.
Principle 2: Flexibility in Use: The design accommodates a wide range of individual preferences and abilities.
2a. Provide choice in methods of use to allow older adults to feel they are in control .
DC: Provide choices of input (e.g., touch, stylus) and navigation methods (e.g., Yes/No (Next/Back) touch buttons, scroll, and swipe gestures). Provide multiple choices of visual (text size, color contrast) and audio (speed, volume) characteristics. Candidate selection could be linear or random access. Provide consistency in system navigation in order to make older adults feel they are in control. Allow for easy reversal of actions (as described in 5c.) and easy access to all the content (main control pane with Review, Instructions, Audio speed, Text size, and Contrast touch buttons).
2b. Accommodate right- or left-handed access and use.
DC: Make any inputs usable for right- or left-handed older adults by making the navigation accessible and touch buttons easy to reach with either left of right fingers.
2c. Facilitate the older adult’ accuracy and precision.
DC: Use large touch-buttons and provide enough space between the buttons. The big size facilitates accuracy by reducing fine finger movements. The whitespace between buttons allows older adults to have a clear idea of the location of the target buttons.
2d. Provide adaptability to the older adults’ pace.
DC: Locate Review and Instruction touch buttons on the main control panel, easily accessible at any point of the voting. Ballot UI should support any voter’s pace (e.g. provide multiple audio speed options, have linear and random access interfaces). Provide a choice for skipping instructions, any races or propositions.
Principle 3: Simple and Intuitive Use: Use of the design is easy to understand, regardless of the user’s experience, knowledge, language skills, or current concentration level.
3a. Eliminate unnecessary complexity.
DC: Provide guided linear or random access structure that matches the audio interface. Locate Review and Instruction touch buttons as described in 2d. The piece-by-piece process breaks down a complex task into several easy-to-complete subtasks to reduce complexity. Remove visual clusters. Avoid multiple contest pages in one screen.
3b. Be consistent with older adults’ expectations and intuition.
DC: Answer with Yes/No (Next/Back) to the question on each page. Design touchscreen buttons to look touchable.
3c. Accommodate a wide range of literacy and language skills.
DC: Use universal/recognizable icons for text size, audio speed, and contrast. Use simple Y for Yes, N for No, and I for instructions. Provide step-by-step instructions how to use the ballot (e.g., how to navigate pages, how to select a candidate).
3d. Arrange information consistent with its importance.
DC: Arrange page information consistent with its importance (e.g., title of the page: president and vice president, voting information: vote for one pair of candidates and name of the candidate). Design instruction pages so that these can be skipped at any point. Arrange these pages based on the importance of the information (page 1: use of the instruction touch button and navigation using Yes/No (Next/Back) touch buttons; page 2: adjusting the audio volume; page 3: adjusting audio speed, text size, and contrast; page 4: navigation between instruction or contest pages; page 5: navigation between candidate or review pages; page 6: use of scroll buttons; page 7: review of the selections; page 8: use of write-in page). Location and background color of ballot progress indicator need to be less distractive but noticeable. Make Yes and No (Next and Back) buttons accessible. These need to stand out visually. Choose a different font sizes to differentiate levels of importance of the context.
3e. Provide effective prompting and feedback during and after task completion.
DC: Provide two ways for verification, a prompt and a sub-review message. A prompt message (e.g., “Are you sure you want to vote for Daniel Court and Amy Blumhardt from the Purple party?”) reverts to the previous question if older adults press No. A sub-review message (e.g., “You voted for Daniel Court and Amy Blumhardt from the Purple party.”) reverts to that specific candidate page if older adults press No. Indicate the progress by color-coding the current candidate. Provide visual and audio prompting and feedback during and after the voting process.
3f. Design dialogs to yield closure .
DC: Interface should provide older adults with the satisfaction of accomplishment and completion, a sense of relief, and an indicator to prepare for the next group of actions.
Principle 4: Perceptible Information: The design communicates necessary information effectively to the user, regardless of ambient conditions or the user’s sensory abilities.
4a. Use different modes (pictorial, verbal, tactile) for redundant presentation of essential information.
DC: Provide simultaneous visual and audio ballot interfaces. Provide tactile indicators for locating the touch buttons. Use universal icons along with redundant cues (e.g., color, text, and symbols).
4b. Provide adequate contrast between essential information and its surroundings.
DC: Use internationally recognizable color-coding (e.g., Yes (Next) touch button is green, and No (Back) touch button is red). Place all other touch buttons on the main control panel (text size, color contrast, audio speed, review, instruction). Provide high contrast (black text on a white background) as a default mode.
4c. Maximize “legibility” of essential information.
DC: Display information in sans serif and in at least two font sizes: 3.0–4.0 mm (the height of an upper case letter in the smaller text size) and 6.3–9.0 mm (the height of an upper case letter in the larger text size); based on the VVSG (Sect. 220.127.116.11.b.) recommendation. Make page title bold.
4d. Differentiate elements in ways that can be described (i.e., make it easy to give instructions or directions).
DC: Provide color-coded visual representation (e.g., match a color of instruction button with instruction pages).
4e. Provide compatibility with a variety of techniques or devices used by people with sensory limitations.
DC: Allow use of three text sizes, where increased text size would be compatible with the use of a magnifier for visually impaired older adults. Accommodate other input devices (e.g., Sip and puff, mouth stick, pedal switch, speech input).
4f. Design for multiple and dynamic contexts .
DC: Implement context-awareness, self-adapting functionalities, and/or universal control feature, which would work regardless of the context and environment. Derive input indirectly from the user.
Principle 5: Tolerance for Error: The design minimizes hazards and the adverse consequences of accidental or unintended actions.
5a. Arrange elements to minimize hazards and errors: most used elements, most accessible; hazardous elements eliminated, isolated, or shielded.
DC: Begin the UI with instructions. Locate Yes (Next) and No (Back) touch buttons as described in 4c. Locate other touch buttons on the main control panel. Locate Review and Instruction touch buttons on the main control panel (easy to find) while isolated from the most used Yes/No (Next/Back) touch buttons.
5b. Provide warnings of hazards and errors.
DC: Provide any warnings (under voting, over voting) to prevent mistakes during a voting process.
5c. Provide fail safe features.
DC: Provide two ways for verification, a prompt and a sub-review message. A prompt message (e.g., “Are you sure you want to vote for Daniel Court and Amy Blumhardt from the Purple party?”) reverts to the previous question if older adults press No. A sub-review message (e.g., “You voted for Daniel Court and Amy Blumhardt from the Purple party.”) reverts to that specific candidate page if older adults press No. Provide a way for changing the vote (Review touch button).
5d. Discourage unconscious action in tasks that require vigilance.
DC: Locate different function of control buttons far apart (e.g., Yes/No (Next/Back) touch buttons).
Principle 6: Low Physical Effort: The design can be used efficiently and comfortably and with a minimum of fatigue.
6a. Allow older adult to maintain neutral body position.
DC: Provide main input buttons at the locations where older adults’ hands are in neutral body position.
6b. Use reasonable operating forces.
DC: Take out the physical buttons and instead use large touch buttons. Provide capacitive touchscreen rather than resistive touchscreen that requires more physical force.
6c. Minimize repetitive actions.
DC: Avoid multiple actions (e.g., double tap, split-tap) and use a single tap.
6d. Minimize sustained physical effort.
DC: Take out the physical buttons and instead use touch-buttons. Use tactile icons to navigate the older adults’ fingers to the location of the touch buttons. Use touch buttons that require only single tap.
Principle 7: Size and Space for Approach and Use: Appropriate size and space are provided for approach, reach, manipulation, and use regardless of user’s body size, posture, or mobility.
7a. Provide a clear line of sight to important elements for any seated or standing older adult.
DC: Place the important information (questions, referendum content, etc.) at the center of the screen. Provide adjustable height of the tablet stand for any seated or standing older adults.
7b. Make reach to all components comfortable for any seated or standing older adult.
DC: Make a tablet detachable from the stand. Provide tilted tablet stand for any seated or standing user.
7c. Accommodate variations in hand and grip size.
DC: Use large touch buttons and large tactile icons on the cover of the screen. Provide sufficient space between buttons for different size of fingers and grip.
7d. Provide adequate space for use of assistive devices or personal assistance.
DC: Use large touch buttons that can be activated using the assistive devices.