For which of the following should a driver stop if requested?

A driver should stop for a school crossing warden because their primary responsibility is to ensure the safety of children crossing the road. The school crossing warden is typically positioned at designated crossing points and uses signals or commands to direct traffic when children are present. This traffic control measure is in place to protect vulnerable pedestrians, particularly young students, as they navigate potentially hazardous roadways. Adhering to the warden's instructions is not just a legal obligation but also a moral one to enhance the safety of children.

In contrast, while a flagman on a road construction site directs traffic for safety reasons, their role pertains specifically to maintaining safe passage through construction areas rather than acting for pedestrian safety. A herdman with a red flag would signify livestock movement, which is important but not as vital as the protection of children at schools. Lastly, a uniformed deliveryman does not possess the authority to direct traffic and thus does not require vehicles to stop in the same way a school crossing warden does.