Department of Signs

For a quick blast of basic iconography.
I once gave this as a lecture theme during a course I was helping to make up as we went along (sorry but that's the reality) at UL (University of Limerick).

A project of assignment I gave to my students was: before you go designing icons for use in software programs, go thee first to the nearest airport, train station, canteen etc. and check and document the available signs.

How do they work?
How clear are they?
How could they be interpreted/misinterpreted?
Your alternative is?

Anyway, enjoy these signs. And ask those quessies. (Mark, your angry cyclops post reminded me of this theme ).