In 2004, Ginny Redish and I, along with Amy Lee, conducted a review of the relevant literature — research by other people — about designing for older adults (people over age 50). Doing this changed my thinking about universal design.
It wasn’t enough to generate design heuristics. We also came up with ways to operationalize them. That is, you can actually test to see if you have implemented these design practices by answering several questions about each heuristic.
Here’s an article from Technical Communication (which, by the way, was the runner-up for best article of the year for that publication) in which we describe the project, list the heuristics, and talk about some of our results in using them.