What action must a driver take when approaching a round blue sign with a white number 30?

The action a driver must take when approaching a round blue sign with a white number 30 is to drive at less than 30 kph. This sign indicates a speed limit or a minimum requirement for travel, which in this case is set at a maximum of 30 kilometers per hour. Adhering to this limit is crucial for maintaining safety on the road, as it helps regulate traffic flow and reduce the risk of accidents, particularly in areas where lower speeds are necessary due to road conditions, pedestrians, or other factors.

Understanding this sign's significance reinforces the importance of compliance with posted speed limits, as these are established for the safety of all road users.