Accessibility is not to be confused 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 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.Fact: date=February 2007 An alternative is to provide "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.

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 generally 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

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