Final answer:
The guideline for workers in areas with traffic flow under 25 mph is chiefly applicable to traffic police, who ensure safety and manage traffic in these zones.
Step-by-step explanation:
The guideline "workers in parking lots and other areas with traffic flow moving <25 mph" is most applicable to D) Traffic police. They are responsible for managing traffic flow and ensuring safety in these areas. This guideline typically pertains to situations where traffic police need to be especially vigilant to protect not only themselves but also walkers, drivers, and anyone who might be present in locations with low-speed traffic flow, such as parking lots or near schools and campuses where pedestrian safety can be a critical issue.