What is the purpose of a "Road Closed" sign?

The purpose of a "Road Closed" sign is to inform drivers that the road is not open due to an obstruction. This sign is critical for maintaining safety by preventing vehicles from entering areas where there may be hazards, such as construction activities, severe weather damage, or accidents blocking the road. By clearly communicating that the road is closed, this sign helps manage traffic flow and directs drivers away from potentially dangerous situations. In instances where an alternate route is necessary, the sign's presence allows for the implementation of appropriate detour signage to guide drivers safely around the obstruction.

The other options suggest purposes that do not accurately reflect the intent of a "Road Closed" sign. It does not indicate that a road is open, signal a detour directly, or warn of upcoming construction, which can lead to confusion regarding the road's status. The primary focus of the sign is unequivocally to inform about the closed status for safety and traffic management.