Accommodating mobility impaired users on Web

1. Introduction

Current situation of accessibility

Worldwide, there are more than 750 million people with disabilities and this number is increasing. It is critical that the Web be usable by anyone, regardless of individual capabilities and disabilities since the World Wide Web is supposed to be a place where everyone has the ability to find information or shop [3].

Website designers should be sure that the web pages can be accessible by everyone no matter who or where. Accessibility, a category of usability, is a software product's ability to be used by people with disabilities, such as motion impairment [3].

From the angle of legal requirement, in recent years, new laws have created incentives for the development of access to computer technology (see Casali & Williges, 1990; Lazzaro, 1993; McCormick, 1994). The most important of these laws, for the purposes of our discussion, are Section 508 of the 1986 Federal Rehabilitation Act and the 1992 Americans with Disabilities Act (ADA). They ensure us that people with disabilities will have equity in the use of electronic and information technology (E&IT).

In April 4, 2000, President Clinton issued a "National Call to Action", on which over 400 companies and non-profit organizations signed. Its purpose was to bridge the digital divide and create digital opportunity for all Americans.

The attention of the United States as well as the world has turned to the issue of information equality and universal access.

However, many Web designers are not aware of the needs of users with disabilities. A significant proportion of users with disabilities can hardly have access to Web due to poor accessibility of Web pages. Moreover, there are many complex customization-related HCI issues that must be resolved. That is why we propose universal design which targets the broadest possible range of user capabilities.

This paper provides guidelines, recommendations, good examples and resource for designing the Web pages for the users with mobility impairment. The remaining part of section 1 analyzes the problems faced by mobility impaired people; section 2 gives general recommendations and goals of improved design; section 3 is about the specific guidelines; section 4 shows some successful websites ; section 5 talks about the future progress; section 6 cites the resources, such as papers and books.

Mobility impairment

By the term "Mobility impairment" we are referring to disabilities that affect the ability to move, manipulate objects, and interact with the physical world. Mobility impaired users include the users who are confined to wheelchair or bed or the people with incapacitated hand movements.

The physical problems the mobility impaired users face include [2]:

• Total lack of muscular control in part or most of the body
• Weakness, such as lack of muscle strength
• Interference with control, where muscles are tense and contracted
• Having problems in accuracy of motor coordination
• Extra, involuntary, uncontrolled and purposeless motion
• Joint movement limitations, small limbs, missing limbs or abnormal trunk size

According to the above problems, we can categorize mobility impaired users into three kinds:

• Level1: users with slightly impaired mobility, such as users with trembling hand
• Level2: users with intermediate impaired mobility
• Level3: users with severe impaired mobility, such as users with locked-in syndrome who are prisoners in their own bodies.

Level1 can be caused by aging and repetitive strain injuries. Level2 may include weakness, spasticity, ataxia and skeletal impairments. Level3 users mainly suffer with paralysis which means total lack of muscular control in part or most of the body.

Mobility impairment can be the result of congenital conditions, accidents, or excessive muscular strain. Some major causes of these impairments are:

• Arthritis. Arthritis is defined as pain in joints, usually reducing range of motion and causing weakness.
• Cerebral Palsy (CP). Cerebral palsy is defined as damage to the motor areas of the brain prior to brain maturity. ). There are more than 750,000 in the U.S. with CP (children and adults), and 15,000 infants are born each year with CP.
• Spinal Cord Injury. Spinal cord injury can result in paralysis or paresis (weakening).
• Head Injury (cerebral trauma). The term "head injury" is used to describe a wide array of injuries, including concussion, brain stem injury, closed head injury, cerebral hemorrhage, depressed skull fracture, foreign object (e.g., bullet), anoxia, and post-operative infections.
• Stroke (cerebral vascular accident; CVA).
• Loss of Limbs or Digits (Amputation or Congenital).
• Parkinson's Disease. This is a progressive disease of older adults characterized by muscle rigidity, slowness of movements, and a unique type of tremor.
• Multiple Sclerosis (MS). Multiple sclerosis is defined as a progressive disease of the central nervous system characterized by the destruction of the insulating material covering nerve fibers.
• ALS (Lou Gehrig's Disease). ALS (Amyotrophic Lateral Sclerosis) is a fatal degenerative disease of the central nervous system characterized by slowly progressive paralysis of the voluntary muscles.
• Muscular Dystrophy (MD).

Because of these physical problems, the chance is good for these users to face the following problems when they visit websites:

• It is very hard for them to use mouse since mouse requires detailed movements compared to keyboard. These users might not be able to interact with the pages due to an inability to maneuver the mouse.
• It is very easy for them to make mistakes when they want to choose a hyperlink and click on it.
• It may not be so easy for them to input via voice input devices because of the control problem of face muscles.
• It is very hard for them to get access to Web if the web pages are not accessible from the keyboard.
• It is not easy for them to hold down multiple keys simultaneously.

User confusion about how to perform tasks is always a problem, but such problems become magnified for users who use alternative input and output devices or who require extra steps or time to navigate, activate controls, or read and enter text. As web designers, we should try our best to accommodate these users on Web.

2. Recommendations

First of all, the key to understanding the problem of accessibility is to understand the needs of users. Designers should employ user centered design approach [4].

To a great extent, improving the accessibility of Web pages for mobility impaired users relies on novel hardware, such as head-mounted pointers (replacing traditional mice) and foot-operated mice. It is very important that software should accommodate the alternative hardware.

The goals of improved design include:

2.1 In order to truly serve users with disabilities, accessibility must mean more than simply providing "direct" access through assistive technologies bundled with software, and more than providing the capability to add such assistive technologies. It also must mean designing user interfaces that are easier to use for users with disabilities as well as users "with out" disabilities by taking their needs into account when web pages are designed.

2.2 Consider the needs of people with disabilities in all stages of the design process and test with the mobility impaired users.

2.3 Eliminate users' sensitivity to tasks by reducing the number of steps or wide range of movement.

2.4 The users with mobility impairment can be empowered by computers to perform tasks that would have been difficult for them with traditional technology.

2.5 The users must be able to access all parts of a web page using something other than the mouse, such as the keyboard.

3. Guidelines

The following guidelines are based on the documentations from [2][6][7][8][9]. They are grouped into four categories.

3.1 Keyboard Navigation

• Keyboard access and accelerators

  According to the above analysis, as for the mobility impaired users, using a mouse is so hard that the software must be accessible via the keyboard, which means that all clickable elements are keyboard accessible. The more keyboard access an application provides, the greater the user's ability to work with that application.

  It is important that web pages provide keyboard access to controls, features, and information in environments that have keyboard navigation. Comprehensive keyboard access helps users who cannot use a mouse. In some cases, extra engineering may be required to ensure that these features work in all areas of an interface. Whenever practical, commonly used actions and application dialogs should be accessible through buttons or keyboard accelerators.

• Good keyboard navigation

  Three new attributes in HTML 4.0 allow Web developers to customize Web pages to make it easier for people who rely on the keyboard to navigate a Web site. They are ACCESSKEY, TITLE attribute and TABINDEX.

  The TAB key moves between links and image map areas in the order they're defined in the HTML. Use the TABINDEX attribute to specify proper keyboard navigation order when necessary. Use the ACCESSKEY attribute to provide access keys for all controls, and for links that act like controls. Underline the access key in the control's label.

  This guideline can be crucial for the people with mobility impairment.

• Tab order

  Use a logical tab order (left to right, top to bottom, or as appropriate for locale). Tab order is the order of jumping among the hyperlinks in a web page by using the tab key.

• Keyboard mapping

  Use of key mappings (see section 6.7) consistent with the local application environment not only speeds use of applications for users with movement difficulties, but it also increases the effectiveness of alternate input technologies such as speech recognition.

• Avoid conflicts

  In order to avoid conflicts with current and future access products, designers should avoid using techniques not compatible with current keyboard accessibility features, which are built into the the Operating Systems or local environment, such as MS Windows or X Windows. These features include reserved keyboard mappings and keyborad enhancements.(see section 6.6 and 6.7)

• Multiple methods

  Where possible, provide more than one method to perform keyboard tasks, such as having access to a hyperlink via tab key or shortcut keys.

• Hot keys

  Designers had better define more function keys (hot keys) to help users use only keyboard to visit Web. Although the tab key can jump between all the clickable items on a web page, we can not go back to the previous page or go forward to the next page by pressing only one special key. Why not define some hot keys to do it? For example, we can define the left arrow key as the back key, and the right arrow key as the forward key for the handicapped users who have difficulty to press more than two keys simultaneously.

• Within the area of one hand

  Hot keys often used together should be a bit apart away to avoid making frequent mistakes due to mobility impairment. However, it also should avoid requiring long reaches on frequently performed keyboard operations for people using one hand.

• Avoid repetitive keypresses

  Designers should avoid requiring users to make repetitive keypresses. Repetitive keypresses will add burden on the users with mobility impairment and especially worsen the situation of repetitive strain injury.

3.2 Assistive Technologies

• Using assistive technologies

  Some users with mobility impairment use assistive technologies to aid their interactions. Common hardware add-ons include alternative pointing devices such as head tracking systems and joysticks.

• Using standard API functions

  Assistive software and hardware mediates the communication between users and applications, making it particularly sensitive to cases where standard API functions are not used. This sensitivity occurs because assistive software such as speech recognition monitors the state and behavior of applications partly by tracking their use of API functions. For this reason, applications that do not use standard API calls have the potential to create serious usability problems for people with disabilities.

• Voice controlled browsing

  Choose the voice devices as the alternative devices. For the users who have difficulty to use their hands, they can input via voice devices. However, it may still be hard for these users to make complex choices. The next guideline will discuss how to provide simple choices.

  When creating web pages for voice navigation, hyperlinks should be easily spoken English text. Image links should be used sparingly. It would be helpful for non-English speaking mobility impaired users if the web pages support alternative input and output devices, such as head control devices.

• Low physical effort

  Low physical effort means that the design can be used efficiently and comfortably and with minimum of fatigue.

3.3 Hyperlink

• Image maps

  Use client-side image maps to simplify keyboard navigation.
  Image maps are images in Web pages that include hotspots. The most common use of image maps is to allow users to access different documents by clicking on different areas in an image. Client-side image map data is stored in HTML files (and can be embedded directly into a page containing other HTML elements). When a visitor to a Web page visits the hotspots via Tab key and Enter key within a client-side image map, the browser processes the map data without interaction with the Web server.

• link text

  Link text should be stand alone, meaningful but brief.

• Hyperlink

  When one hyperlink is highlighted, it should become bigger so that it is easier for the user to click on it.

3.4 Other

• Alternate pages

  Designers should create a "text-only" version of their websites and also provide alternate pages. The alternate pages are to support alternative input or output devices.

• Categorize

  Easy choice means that users can answer "yes" or "no" to make a choice. To achieve this goal, designers should focus on how to categorize the information and present the information so that clear questions and easy choices can be provided.

• Menu structure

  Designers should avoid placing frequently used functions deep in a menu structure since it requires more operations and frustrates the users.

• Multiple modalities

  Web pages should be designed to present and accept information in multiple modalities.
  Environments are needed that allow users to tailor system input and output modalities to their capabilities and preferences. Recent research has suggested that information can be represented in a form abstracted from the particulars of its presentation. The technical solution of providing multiple redundant interface input and output mechanisms is not, in itself, sufficient to resolve conflicting user needs. In the absence of any means for intelligently designing and customizing their use, highly multimodal interfaces could lead to as many usability problems as they resolve, causing some users to trip over features designed to help other users. Determining how users will interact with such systems is a challenging HCI issue.

TABLE1 Correspondence between guidelines and levels

4. Websites

• http://www.ictaglobal.org/
  This is the website of the International Commission on Technology and Accessibility. Last access on April 24, 2001.
  • On this website, we can use tab key to reach all the links which can be clicked on by press "Enter".
  • It is approved by Bobby test(http://www.cast.org/bobby/).
  • On this website, all images have ALT text.
  • The font size is large. It is convenient for the users to click on the links.
  • The design is so simple that it helps to reduce the number of operations and mistakes.
    
• http://www.mdausa.org/
  This is the website of the Muscular Dystrophy Association. Last access on April 24, 2001.
  • It has site map, which can help to reduce the number of operations.
    
    
    FIGURE1 Part of the site map from http://www.mdausa.org/
    
    
  • The highlighted links will change color and the corresponding font size will become larger, which helps the users to click the links and make fewer mistakes.
  • It supports search to locate the information as fast as possible.
  • All images have ALT attribute.
    
• http://www.hrdc-drhc.gc.ca/student_loans/common/index.shtml
  This is the website of Canada student loans program. Last access on April 17, 2001.
  • It provides bitmap pictures for several often used links, which helps the users to click the links and make fewer mistakes.
    
    
    FIGURE2 Bitmap links from http://www.hrdc-drhc.gc.ca/student_loans/common/index.shtml
    
    
  • It supports search to locate the information as fast as possible.
  • It has site map, which can reduce the number of operations.
  • ALT attribute is used.
    
• http://www.speechworks.com/
  Speechworks is a company which is dedicated to the technology of over-the-telephone speech recognition. Last access on April 24, 2001.
  • The menu will remain on the left wherever the users are on the website, which helps the users to jump to any other section directly.
  • It has site map, which can reduce the number of operations.
  • It supports search to locate the information as fast as possible.
  • It provides the products for voice input.
  • It provides alternate pages in French, German, and Spanish.
• http://mirror.subotnik.net/jkorpela/forms/accesskey.html
  Last access on April 24, 2001.
  • It gives detailed tutorial about ACCESSKEY.
  • It has set ACCESSKEY for keyboard only navigation.
  
  
  FIGURE3 Example of Accesskey from http://mirror.subotnik.net/jkorpela/forms/accesskey.html
  This figure is a simple form which has accesskeys for all fields. Accesskey allows users to trigger a function only by the keyboard. For example, after filling in all the fields, if the users want to mail the message, they can press Alt-m instead of pressing the button of "Mail Message".
• http://www.pipebeach.com
  Last access on April 22, 2001.
  • PipeBeach helps people to speak with the Web using telephone. PipeBeach is developing a server product called speechWeb. This is a solution whereby a voice service (used from a telephone) can be designed using web alike technology. The work is based on the upcoming W3C standard called VoiceXML. In VoiceXML, speech synthesizers and recognizers are used to interact with the users.
• http://www.tellme.com
  Last access on April 24, 2001.
  • Tellme provides large voice application network by combining the power of the Internet with the ubiquity of the telephone. It's work is also based on VoiceXML.

5. Conclusions

While current direct and assistive access capabilities are positive steps, much more can be done to improve accessibility for the mobility impaired users.

In the future, there are several tasks to undertake:

• Researchers should study on the real need of the mobility impaired users.
• Since the users with mobility impairment often need alternative means of interacting with the systems, future operating system infrastructures must be designed with accessibility in mind and assistive technology should be paid more attention.
• The accessibility of current web pages should be checked, analyzed and enhanced.
• More specific guidelines should be provided for the mobility impaired users.
• Standards about hardware and software should be proposed as soon as possible, for example, the standard of the definitions of hot keys.
• Practitioners should really use the guidelines and standards when they design the web pages.
• The HCI issue of determining how mobility impaired users will interact with the systems is a challenge for the researchers. It is because the technical solution of providing multiple redundant interface input and output mechanisms is not, in itself, sufficient to resolve conflicting user needs. In the absence of any means for intelligently designing and customizing their use, highly multi-modal interfaces could lead to as many usability problems as they resolve, causing some users to trip over features designed to help other users.
• Researchers should explore more common website architectures for their study.

Looking farther in the future, maybe we have to think about how to really design an interface for all kinds of users although some researchers have proposed the adaptive interfaces along with intelligent agents.

Whatever, statistics has shown that there is a growing market for accessible computer products.

In a word, we may claim that universal usability or accessibility of web pages have made an opportunity for the websites, made an opportunity for new technology, and made an opportunity for the Computer Industry.

6. Resources

• http://www.apple.com/disability/physical/
  Last access on April 17, 2001.
• http://www.cast.org/bobby/
  This is a free service to help Web page authors identify and repair significant barriers to access by individuals with disabilities. Last access on April 17, 2001.
• http://www.microsoft.com/enable/msaa/default.htm
  Microsoft Active Accessibility is a developer technology that can be used to test the accessibility. Last access on April 17, 2001.
• http://www.webable.com/
  WebABLE is a leading provider of Web accessibility technology, consulting, and training. Last access on April 17, 2001.
• http://www.design.ncsu.edu:8120/cud/univ_design/princ_overview.htm
  This website contains seven principles about web page design. Last access on April 17, 2001.
• http://www.microsoft.com/enable/dev/web/guidelines_IE-u.htm
  It explains the accessibility of Internet Explore. Last access on April 17, 2001.
• http://www-3.ibm.com/ibm/easy/eou_ext.nsf/publish/558
  IBM Ease of Use. Last access on April 17, 2001.
• http://www.w3.org/TR/WAI-WEBCONTENT/full-checklist.html
  http://www.microsoft.com/enable/dev/web/checklist-u.htm
  These two links give the checklist for testing the Web pages for accessibility. Last access on April 17, 2001.

• http://www.w3.org/TR/WAI-WEBCONTENT-TECHS/
  W3C. Last access on April 17, 2001.
• http://www.ictaglobal.org/
  The International Commission on Technology and Accessibility (ICTA). Last access on April 17, 2001.
• http://www.resna.org/
  The Rehabilitation Engineering & Assistive Technology Society of North America (RESNA). Last access on April 17, 2001.
• http://www.aota.org/
  American Occupational Therapy Association (AOTA). Last access on April 17, 2001.
• http://www.hcibib.org
  HCI Bibliography : Human-Computer Interaction Resources. Last access on April 17, 2001.
  

1. Rainer Malkewitz. Head Pointing and Speech Control as a Hands-Free Interface to Desktop Computing. Proceedings of the third international ACM conference on Assistive technologies, pp182-188. Marina del Rey, CA USA. 1998.
2. Kevin Christian, Bill Kules, Ben Shneiderman and Adel Youssef. A comparison of voice controlled and mouse controlled web browsing. The fourth international ACM conference on Assistive technologies, pp72-79. Arlington, VA USA.2000.
3. Steven G. Mason, Ziba Bozorgzadeh and Gary E. Birch. The LF-ASD brain computer interface: on-line identification of imagined finger flexions in subjects with spinal cord injuries. The fourth international ACM conference on Assistive technologies, pp109-113. Arlington, VA USA. 2000.
4. Melody M. Moore and Philip R. Kennedy, Human factors issues in the neural signals direct brain-computer interfaces. The fourth international ACM conference on Assistive technologies, pp114-120. Arlington, VA USA. 2000.
5. Edmund LoPresti, David M. Brienza, Jennifer Angelo, Lars Gilbertson and Jonathan Sakai. Neck range of motion and use of computer head controls. The fourth international ACM conference on Assistive technologies, pp121-128. Arlington, VA USA. 2000.
6. Simeon Keates, John Clarkson and Peter. Investigating the applicability of user models for motion-impaired users. The fourth international ACM conference on Assistive technologies, pp129-136. Arlington, VA USA. 2000.

• IntelliTools, Inc.
  • Click It!
    This is the Keyboard access to menu bar items.
  • Intellikeys
    This is the alternate keyboard for the people who have difficulty using a standard keyboard.
• Apple
  The Mac operating system features built-in technology enabling the user to use the numeric keypad for mouse movement, keyboard with one finger or a mouthstick, and prevent repeating keys. There are dozens of different kinds of expanded keyboards, switches and input devices giving people with mobility impairment access to the Macintosh.
• Eye-tracking, gaze-detecting controllers
  These controllers have been developed by several researchers and companies who make devices to assist the handicapped. Applications for the physically handicapped have been successful in enabling bedridden, paralyzed, or otherwise disabled people to broaden the horizons of their life. They can control wheelchairs, operate equipment, or use personal computers for a variety of tasks.
• Operating Systems
  MS Windows, OpenWindows, and Motif all provide keyboard navigation.
• IE 4.0
  Internet Explore 4.0 can support the three new attributes in HTML 4.0 which are ACCESSKEY, TITLE and TABINDEX. For example, the combination of Alt key plus right arrow key means forward and the combination of Alt key plus left arrow key means back.
• WiViK
  It is the Windows Visual Keyboard from Prenke-Romich company and supports the creation and adaptation of graphical virtual keyboard emulators for the Brain-Computer Interface.
• Assistive Technologies
  Alternate Pointing Device: Gives users with limited or no arm and hand fine motor control the ability to control mouse movements and functions. Examples include foot operated mice, head-mounted pointing devices and eye-tracking systems.
• Screen Keyboard
  On-screen keyboard provides the keys and functions of a physical keyboard and is typically used in conjunction with alternate pointing devices.
• Predictive dictionary
  Predictive dictionaries speed typing by predicting words as the user types them, and offering those words in a list for the user to choose. Originally intended for users with movement related disabilities, predictive dictionaries are now becoming popular for users with RSI and as a way to boost typing speed.
• Speech Recognition It allows the user with limited or no arm and hand fine motor control to input text and/or control the user interface via speech.

• StickyKeys
  StickyKeys Provide looking or latching of modifier keys (e.g., Shift, Control) so that they can be sued without simultaneously pressing the keys. This allows single finger operation of multiple key combinations.
• MouseKeys
  Using mouseKeys is an alternative to the mouse which provides keyboard control of cursor movement and mouse button functions.
• RepeatKeys
  RepeatKeys Delay the onset of key repeat, allowing users with limited coordination time to release keys.
• SlowKeys
  Using slowKeys Requires a key to be held down for a set period before keypress acceptance. This prevents users with limited coordination from accidentally pressing keys.
• BounceKeys
  Using bounceKeys Requires a delay between keystrokes before accepting the next keypress so users with tremors can prevent the system from accepting inadvertent keypresses.
• ToggleKeys
  ToggleKeys indicate locking key state with a tone when pressed, e.g., Caps Lock.

• The keyboard Mapping of "5 consecutive clicks of Shift key" is reserved for On/Off for StickyKeys.
• The keyboard Mapping of "Shift key held down for 8 seconds" is reserved for On/Off for SlowKeys and RepeatKeys.
• The keyboard Mapping of "6 consecutive clicks of Control key" is reserved for On/Off for screen reader numeric keypad.
• The keyboard Mapping of "6 consecutive clicks of Alt key" is reserved for Future Access use.

1. "Web Accessibility for People With Disabilities" This is a book written by Michael G. Paciello, which is a vital tool for Web site developers and administrators.
2. "User Interfaces for All: Concepts, Methods, and Tools", edited by Constantine Stephanidis, Lawrence Erlbaum Associates, Inc. http://www.erlbaum.com. Last access on April 17, 2001.

• news: alt.support.post-polio
• news: su.org.disabled

[1] Physical/Motor, http://www.apple.com/disability/physical/, last access on April 17, 2001.
[2] Designing more usable Web sites, http://www.trace.wisc.edu/world/web/, last access on April 17, 2001.
[3] MSDN online Web workshop, http://msdn.microsoft.com/workshop/design/layout/accessible.asp, last access on April 17, 2001.
[4] Lila F. Laux, Peter R. McNally, Michael G. Paciello, Gregg C. Vanderheiden. Designing the World Wide Web for People with Disabilities: A User Centered Design Approach. ASSETS'96, pp94-101. Vancouver, British Columbia, Canada.
[5] Ben Shneiderman. Designing the User Interface: strategies for effective human-computer interaction. Third Edition. Addison-Wesley. 1998.
[6] Web Content Accessibility Guidelines 1.0, http://www.w3.org/TR/WAI-WEBCONTENT/, last access on April 17, 2001.
[7] Microsoft accessibility, http://www.microsoft.com/enable/dev/web/, last access on April 17, 2001
[8] IBM accessibility center, http://www-3.ibm.com/able/accessweb.html, last access on April 17, 2001
[9] Eric Bergman, Earl Johnson, Towards Accessible Human-Computer Interaction, http://www.sun.com/access/developers/updt.HCI.advance.html, last access on April 24, 2001