What action must a driver take when approaching a round blue sign with the number 30 on it?

When approaching a round blue sign with the number 30, the driver understands that this indicates a specific speed limit of 30 kilometers per hour. In this context, the sign serves as a regulatory measure to ensure safety on the road, especially in areas where slower speeds are critical due to high pedestrian activity or road conditions.

The action required by the driver is to not exceed 30 kilometers per hour, ensuring compliance with the speed limit for safety. Additionally, the instruction implies that if conditions permit, the driver should also not be traveling below this speed, as driving too slowly could hinder traffic flow and create dangerous situations, particularly in zones where maintaining a minimum speed is essential for smooth operations.

This understanding reinforces the dual responsibility of the driver: to respect the upper limit of speed (not exceeding 30 kph) and to adhere to a minimum operational speed when safe to do so, thus promoting both safety and efficiency on the roads.