Which combination describes a permissible action typically indicated by a permissive sign?

The option describing a permissible action typically indicated by a permissive sign is associated with allowing certain movements or behaviors on the road. In this context, permissive signs communicate to drivers that specific actions are permitted.

For instance, a sign indicating "turn allowed" suggests that drivers are permitted to make a turn, which is a clear example of a permissive action. This type of sign provides essential information that facilitates smooth traffic flow by informing drivers of safe and legal maneuvers they can perform.

Other options present actions that do not align with the concept of permissive signs. A stop action indicates a requirement to halt, which is not a permission but an instruction. Speeding actions would generally be in violation of traffic laws, as there are usually speed limits established. A parking prohibition simply indicates that parking is not allowed in a specific area, which again does not denote a permissive action. Hence, "turn allowed" is the combination that accurately reflects the essence of what a permissive sign conveys to drivers.