Accessibility is a general term used to describe the degree to which a product (e.g., device, service, environment) is accessible by as many people as possible. It is not to be mixed up with usability which is used to describe the extent to which a product (e.g., device, service, environment) can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use. Accessibility can also be viewed as the "ability to access" the functionality, and possible benefit, of some system or entity; such a definition brings in access-based individual rights laws and regulations that are discussed below. One meaning of accessibility specifically focuses on people with disabilities and their right of access to entities, often through use of assistive devices such as screen-reading web browsers or wheelchairs. Other meanings are discussed below.

Accessibility is strongly related to universal design when the approach involves "direct access." This is about making things accessible to all people (whether they have a disability or not). However, products marketed as having benefited from a Universal Design process are often actually the same devices customized specifically for use by people with disabilities. An alternative is to give "indirect access" by having the entity support the use of a person's assistive technology to achieve access (e.g., screen reader).

Disabilities

The disability rights movement advocates equal access to social, political, and economic life which includes not only physical access but access to the same tools, services, organizations and facilities which we all pay for.This is the internationally recognized symbol for accessibility

While it is often used to describe facilities or amenities to assist people with disabilities, as in "wheelchair accessible", the term can extend to Braille signage, wheelchair ramps, elevators, audio signals at pedestrian crossings, walkway contours, website design, and so on.

Various countries have legislation requiring physical accessibility which are (in order of enactment):

In the US, under the Americans with Disabilities Act of 1990, new public and private business construction typically must be accessible. Existing private businesses are required to increase the accessibility of their facilities when making any other renovations in proportion to the cost of the other renovations. The U.S. Access Board is "A Federal Agency Committed to Accessible Design for People with Disabilities." Many states in the US have their own disability laws.

In Australia, Disability Discrimination Act 1992 has numerous provisions for accessibility.

In the UK, the Disability Discrimination Act 1995 has numerous provisions for accessibility.

In South Africa The Promotion of Equality and the Prevention of Unfair Discrimination Act 2000 has numerous provisions for accessibility.

In Ontario, Canada, the Ontarians with Disabilities Act of 2001 is meant to "improve the identification, removal and prevention of barriers faced by persons with disabilities..."

Transportation

In transportation, accessibility refers to the ease of reaching destinations. People who are in places that are highly accessible can reach many other activities or destinations quickly, people in inaccessible places can reach many fewer places in the same amount of time.

A measure that is often used is to measure accessibility in a traffic analysis zone i is:

where:

i = index of origin zones

j = index of destination zones

= function of generalized travel cost (so that nearer or less expensive places are weighted more than farther or more expensive places).

For a non-motorized mode of transport, such as walking or cycling, the generalized travel cost may include extra factors such as safety or gradient.

Automobile accessibility also refers to ease of use by disabled people.

Accessibility planning

In the United Kingdom, the Department for Transport have mandated that each local authority produce an Accessibility Plan that is incorporated in their Local Transport Plan. An Accessibility Plan sets out how each local authority plans to improve access to employment, learning, health care, food shops and other services of local importance, particularly for disadvantaged groups and areas. Accessibility targets are defined in the accessibility plans, these are often the distance or time to access services by different modes of transport including walking, cycling and public transport.

Accessibility Planning was introduced as a result of the report "Making the Connections: Final Report on Transport and Social Exclusion". This report was the result of research carried out by the Social Exclusion Unit.

Housing

Most existing and new housing, even in the wealthiest nations, lack basic accessibility features unless the designated, immediate occupant of a home currently has a disability. However, there are some initiatives to change typical residential practices so that new homes incorporate basic access features such as zero-step entries and door widths adequate for wheelchairs to pass through.

Great Britain applies the most widespread application of home access to date. In 1999, Parliament passed Section M, an amendment to residential building regulations requiring basic access in all new homes. ("Doors to Be Swept Away in New Rules for Builders", Rachel Kelley, The Times, December 5, 1997.) In the United States, the 1988 Amendments to the Fair Housing Act added people with disabilities, as well as familial status, to the classes already protected by law from discrimination (race, color, sex, religion and country of origin). Among the protection for people with disabilities in the 1988 Amendments are seven construction requirements for all multifamily buildings of more than four units first occupied after March 13, 1991. These seven requirements are as follows:

An accessible building entrance on an accessible route.

Accessible common and public use areas.

Doors usable by a person in a wheelchair.

Accessible route into and through the dwelling unit.

Light switches, electrical outlets, thermostats and other environmental controls in accessible locations.

Reinforced walls in bathrooms for later installation of grab bars.

Usable kitchens and bathrooms.

(From Fair Housing First, a website sponsored by the U.S. Department of Housing and Urban Development).

In spite of these advancements, the housing types where most people in the United States reside --single-family homes--are not covered by the Americans with Disabilities Act, the Fair Housing Act, or any other federal law with the exception of the small percentage of publicly-funded homes impacted by Section 504 of the Rehabilitation Act. As a result, the great majority of new single-family homes replicate the barriers in existing homes.

The broad concept of Universal Design is relevant to housing, as it is to all aspects of the built environment. Furthermore, a Visitability movement begun by grass roots disability advocates in the 1980s focuses specifically on changing construction practices in new housing. This movement, a network of interested people working in their locales, works on educating, passing laws, and spurring voluntary home access initiatives with the intention that basic access become a routine part of new home construction.

Telecommunications and information technology access

A further dimension of accessibility is the ability to access information and services by minimizing the barriers of distance and cost as well as the usability of the interface. In many countries this has led to initiatives, laws and regulations that aim toward providing universal access to the internet and to phone systems at reasonable cost to citizens.

Currently there are a few major movements to coordinate a set of guidelines for accessibility for the web. The first and most well known is The Web Accessibility Initiative (WAI), which is part of the World Wide Web Consortium (W3C). This organization developed the Web Content Accessibility Guidelines (WCAG) 1.0 which explains how to make Web content accessible to people with disabilities. Web "content" typically refers to the information in a Web page or Web application, including text, images, forms, sounds, and such. (More specific definitions are available in the WCAG documents.)

The WCAG is separated into 3 levels of compliance, A, AA and AAA. Each level requires a stricter set of conformance guidelines, such as different versions of HTML (Transitional vs Strict) and other techniques that need to be incorporated into your code before accomplishing validation. Online tools such as the Watchfire WebXACT engine or the imergo Web Compliance Manager will allow users to submit their website and automatically run it through the WCAG guidelines and produce a report, stating whether or not they conform to each level of compliance. Adobe Dreamweaver also offers plugins which allow web developers to test these guidelines on their work from within the program.

A further source of web accessibility guidance comes from the US government. Section 508 of the US Rehabilitation Act is a comprehensive set of rules designed to help web designers make their sites accessible. They've also developed a website where you can take online training course for free to learn about these rules. 508 Universe

In general, for a website to comply with accessibility standards, they should at least have the following:

(X)HTML Validation from the W3C for the pages content

CSS Validation from the W3C for the pages layout

At least WAI-AA (preferably AAA) compliance with the WAI's WCAG

Compliance with all guidelines from Section 508 of the US Rehabilitation Act

Access keys built into the HTML

Semantic Web Markup

A high contrast version of the site for individuals with low vision

Alternative media for any multimedia used on the site (video, flash, audio, etc)

A further good idea is for websites to include a web accessibility statement on the site. This page details the accessible status of the page, lists access keys and can display which validations have been achieved for the site as well as include their pledge for accessibility. Example of a accessibility statement