A recent set of experiments regarding road signs and other warning signs has yielded some interesting results.
The experiments, there were four in all, involved comparing people's reactions to highly dynamic warning signs and warning signs that are not very dynamic. What does it mean for a warning sign to be dynamic? The more motion a sign conveys, the more dynamic the sign is. For example, a sign with a running person on it would be more dynamic than a sign with a walking or standing person on it.