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

The action indicated by a blue sign with a white number 30 typically signifies a minimum speed limit, specifically set at 30 kilometers per hour (kph). This means that drivers are required to maintain a speed of at least 30 kph and should not drive slower than that unless conditions (such as severe weather or congestion) warrant it.

When presented with this sign, drivers are expected to be aware that driving slower than the designated limit can create hazards, particularly on roads where maintaining a certain speed is necessary for safety and traffic flow. Consequently, if a driver is unable to maintain this minimum speed, it may be advised to refrain from using that road until they are able to comply with the speed limit or until conditions allow for safe navigation at the required speed.

Therefore, both aspects of the provided answer correctly encapsulate the responsibilities of drivers upon encountering this sign. The need to avoid traveling slower than 30 kph, alongside the notion of staying off the road if unable to comply, reflects the dual nature of maintaining safety on the road.