The concept has been around for over 50 years. It is a set of ideas meant to create buildings, products and environments that are inherently accessible to older people, people without disabilities and people with disabilities. ALL PEOPLE (even children).
One of the sessions I attended at last year’s Built Green Conference in Seattle was led by Dave Porter (PorterWorks) who actually built his entire home around both green and universal design concepts. (See Going Green at The Beach) One of the first things Dave asked was, who decided why the light switch was located where it is – or the wall outlet’s location in height above the floor. Even the direction that a door opens makes a huge difference. Especially for someone using crutches or a wheelchair. It gave me a lot to think about and I bought a couple of books I am still reading.
So until I have a lot more to say on the subject, read something by a professional: “Universal Bath Design: Light Your Bathroom for All Ages and Abilities”