Final answer:
A green circle with a straight arrow pointing upwards on a sign means to 'Go straight.' This type of sign utilizes a universally recognized symbol to give clear driving instructions.
Step-by-step explanation:
A sign depicting a green circle with a straight arrow pointing upwards inside it means 1) Go straight. Road signs are designed to provide clear, simple directions for drivers to follow for safe driving. In this case, the arrow indicating 'upwards' or 'forward' is a universally recognized symbol that instructs drivers to continue in the same direction they are currently traveling, without making any turns.