It turns out that there is. Scienceblogs posted earlier this month* about a study from the Journal of Physical Activity and Health in which researchers posted a sign next to the elevator on a college campus which said “Walking up stairs burns almost 5 times as many calories as riding an elevator." The sign also indicated the directions to the nearest stairs and had a cartoon of the school's mascot taking the stairs. The results were that the use of the stairs increased for both stairs which were plainly visible nearby and those which were hidden from view -- there was an overall increase of 34% that lasted one month after the signs came down! This is a great example of how research can be done ... have your students try to figure out how to gather the data. The original journal article can be found here.
*(I completely missed this on Scienceblogs, which I normally follow closely, but spotted it today on Dan Pink's blog.) -- Posted by Steve.