the no pedestrian access - general public EME warning sign is used on shared facilities to identify areas that exceed the general public exposure limits  in a comtrolled area. Th most common example of this is a walkway in front of the transmitting attennas. 

the sign is to be installed at a point prior to entering the hazard zone. It may also be used in circumstances such as a very large roofop area with multiple access areas or poor access restriction