Let’s re-visit Mr. Mace’s speech as he saw Universal Design (UD) and Access, and look at some other related definitions that I think you will appreciate.
This time I thought we’d look back into history in an effort to help clarify these definitions and especially for the benefit of our newer design students and Universal Design (UD) enthusiasts. There is often confusion as to what the definition of Universal Design is and especially what it is in housing. What better resource to help clarify, than the late Architect Ron Mace. Even after 30 years there continues to be confusion between these terms. At an international conference titled “Designing for the 21st Century: An International Conference on Universal Design”, held at Hofstra University in 1989, Ron Mace, the “Father of Universal Design” explained the similarities and differences between Barrier Free, Universal Design and Assistive Technology .in this speech. His comments are quoted directly as follows.
The Innovator of Universal Design, Mr. Ron Mace explained differences between Universal Design and Barrier Free in 1989. Mr Mace is quoted here.
“First, I think it is important that we know the differences between these three things so we can go out and help industry and other people understand some of the subtle but important distinctions between them. When they get muddled, the message becomes vague”
“Barrier-free Design is what we used to call the issue of access. (Accessible design) It is predominantly a disability-focused movement. Removing architectural barriers through the building codes and regulations is barrier-free design. The ADA standards are barrier-free design because they focus on disability and accommodating people with disabilities in the environment. In fact, the ADA is now 1989 (the new most recent ADA, version 2010 is in use as of 2014) the issue of access in the USA. So what is the difference between barrier-free design and universal design? ADA is the law, but the accessibility part, the barrier-free design part, is only a portion of that law. This part of the law, however, is the most significant one for design because it mandates what we can do and facilitates the promotion of universal design. But it is important to realize and remember that barrier-free and ADA is not universal design. I hear people mixing it up, referring to ADA and universal design as one in the same, this is not true”
“Universal Design broadly defines the user. It’s a consumer market driven issue. Its focus is not specifically on people with disabilities, but for all people. It actually assumes the idea that everybody has a disability (at some time in life) and I feel strongly that’s the case. We all become disabled as we age and lose the ability, whether we want to admit it or not. It is negative in our society to say, “I am disabled” or “I am old.” We tend to discount people who are less than we popularly consider to be “normal.” To be normal is to be perfect, capable, competent, and independent. Unfortunately, designers in our society also mistakenly assume that everyone fits this definition of normal. This is just not the case”
“Now, assistive technology to me is really personal use devices, those things focused on the individual, things that compensate or help one function with a disability. Another example of assistive technology is my wheelchair (Mr. Mace used a wheelchair) I need it as an individual. It is not a consumer product. It’s for me. It’s an assistive technology device. Assistive technology really started in the medical industry with durable medical equipment. Here again, people needing equipment are discounted as not being whole people. We are considered to be “patients”. We should be grateful to have an oxygen system that keeps us breathing or a wheelchair that provides mobility. Whether or not the product looks nice, is easy to live with, or is available at a marketable price is unimportant to those developing and providing it, or to those of us who have to use it.”
“So, if you could separate barrier-free, universal design and assistive technology distinctly, they would look like this: assistive technologies are devices and equipment we need to be functional in the environment. Barrier-free, ADA, and building codes are disability mandates; and universal design is design for the built environment and consumer products for a very broad definition of the user that encourages attractive, marketable products that are usable by everyone. The reality is however, that the three blend and move into each other.”  Those are Mr. Mace’s original comments and were not edited here.
Definitions of Universal Design (UD) as it continues to evolve.
The following study is by Schwab and represents his point of view as UD should be focused on the process to be effective as a design tool.The following explains how.
Now let’s look into some more recent definitions in an effort to clarify complexities within the definition of UD. In his book titled: Universal and Accessible Design for Products, Services and Processes , Prof. Robert Erlandson, a design engineer forwards excellent thoughts on universal design and worldwide applications for environments, product, system and other process designs,including education and healthcare.
He notes “The definition of universal design includes the notions of usability and accessibility. Usability and accessibility are not the same.” 
“Usability is multifaceted, it has these 5 attributes:
1) The system should be easy to learn with users being able to quickly get started.
2) The system should be efficient in that once learned, the user can be productive.
3) The system should be easy to remember so that the casual user can return to the system after a short absence and use it without relearning.
4) The system should have a low error rate, that is, users should make few errors during use and easily recover from any errors that are made. Catastrophic errors should not occur.
5) Finally, the system should be pleasant to use so that users are subjectively satisfied when they use it, in other words, they like it.” 
Implied in this expression of usability is that the system is accessible; that is, the user can physically access the system. Usability and accessibility are related but are different attributes of the designed entity. Usability implies accessibility in that if the user cannot physically access the system, then the system is, by default, not usable. Yet accessibility does not imply usability. For example, a person may be able to access a home but if she cannot use the kitchen or bathroom it is not usable. 
As stated in the definition of Universal Design, (see above) UD is intended to be usable to the greatest number of people possible. Usability is in fact one of the seven primary factors in determining, if the principles of UD have been implemented when designing an entity (product, service, process or environment. (Principles of UD will be discussed in another post)
“Accessible design is the design of entities (products ,services and environments) that satisfy specific legal mandates, guidelines, or code requirements with the intent of providing accessibility to the entities for individuals with disabilities”. This is an expansion of the 1991 Center for Accessible housing’s definition which referred only to code requirements. (Later changed to the Center for Universal Design.)
But access guidelines can sometimes conflict with the needs of various users and are not always usable by everyone. For example when curb cuts in city streets were first mandated they didn’t have tactile warnings as they do today, so blind people were unknowingly walking into the street. There were similar problems with braille controls located too low in elevators. They were low enough for people who used wheelchairs, as legally mandated for mechanical devices in a building, but they were found to be difficult for an ambulatory (standing) blind person to locate because they were lower.
Universal “designing” is the process used to resolve these conflicts based on the seven principles of universal design.
Adaptable designsare modifications made to standard design for the purpose of making the design usable for an individual as needed. This definition focuses on modifications that can later be made to make it accessible to people with disabilities, should the need ever arise.
3 J. Nielson, Usability Engineering. San Francisco, CA: Morgan Kaufmann Publishers, 1993.
4. Center for Accessible housing, Definitions: Accessible, Adaptable, and Universal Design (Fact sheet), North Carolina State University, Raleigh, NC, 1991. The center is no longer an active organization.
Blog by Charlie M. Schwab Architect, Universal Design Certified Professional (NARI),
Mr. Schwab is a home designer and licensed Architect specializing in universal and accessible design that is also sustainable and healthy. He also designs light commercial buildings.
View all posts by Charles