What is the primary role of flag persons located on highways and in work zones?

The primary role of flag persons located on highways and in work zones is to stop, slow, or guide traffic safely through construction areas. They play a crucial part in ensuring the safety of both drivers and construction workers by effectively managing the flow of traffic around potentially hazardous work zones.

Flag persons use visual signals, such as flags or lights, and verbal instructions to communicate with drivers, indicating when it's safe to proceed and when they need to stop. Their presence is vital during construction or maintenance activities, where normal traffic patterns are disrupted, and the risk of accidents increases.

In contrast, the other options do not accurately reflect the responsibilities of flag persons. For instance, directing traffic to park relates more to parking lot management rather than highway or work zone control. Controlling speed limits is the responsibility of law enforcement and traffic sign regulation, and inspecting construction materials falls within the purview of construction supervisors and safety inspectors rather than flag persons. Thus, the correct answer highlights the essential function of flag persons in maintaining safety and order in active work zones.