# Accessibility

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Accessibility is a general term used to describe the degree to which a system is usable by as many people as possible without modification. It is not to be confused with usability which is used to describe how easily a thing can be used by any type of user. One meaning of accessibility specifically focuses on people with disabilities and their use of assistive devices such as screen-reading web browsers or wheelchairs. Other meanings are discussed below.

Accessibility is strongly related to universal design in that it is about making things as accessible as possible to as wide a group of people as possible. 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. It is rare to find a Universally Designed product at the mass-market level that is used mostly by non-disabled people; Oxo Good Grips housewares are continually held up as an example.

## 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, organisations 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, audio signals at pedestrian crossings, walkway contours, website design, and so on.

Various countries have legislation requiring physical accessibility:

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

$Accessibility_i = \sum_j {Opportunities_j } f\left( {C_{ij} } \right)$ where:

• i = index of origin zones
• j = index of destination zones
• f(Cij) = function of generalized travel cost (so that nearer (or less expensive) places are weighted more than farther or more expensive places).

For a non-motorised mode of transport, such as walking or cycling, the generalised travel cost may include additional factors such as safety or gradient.