Emblem could be much more effective in communicating the message. Iconic, easily recognizable, image, verbal message and the use of symbolic meanings united on one plane catch attention and explain themselves each other in a more dynamic and fast way.
The followings are the main conclusive points of semiotician T.Sebeok's report on the problem:
1. "Each mode of communication - iconic, indexical, symbolic (or emblematic) - has a set of advantages and a corresponding set of disadvantages, which are both context-bound. Since the context is far from predictable at any stage over the next 10,000 years, and with the passage of time, is bound to become increasingly equivocal, it will be recommended that all signs be constructed of a mixture of the three modes. While this intermingling will still not be fail-safe, it is certain that the more redundancy is built into the system, the more this will tend to ensure accurate decoding by any destination.
2. The perception image-based coding varies across species, cultures and times. Images should be used, but selected with extreme forethought, and should always be incorporated into a framework that judiciously intermingles icons with symbols, supplementing the pair with indexes whenever is feasable.
3. Human senses register only a small portion of ambient stimuli. It is very difficult to foretell what sensory prostheses will be at man's disposal in future decades and centuries. Here again redundancy offers the best hope; all channels that seem technically feasible should be utilized. Take a look at the existing Keep Out emblems that in out opinion could be the base for further development of the message.