One of the most important aspect of commercial design is signage, which is one of the best way of communication and delivering a message directly to the audience. Most of these signs are created for Wing Hop Fung, which I worked as in-house designer, then the creative director.
No matter what the purpose of any signage is, the most important thing about them stays the same: to tell people what to do and what not to do. I find icons works the best on any simple communication in situations like this.