How can an officer indicate they are in command of a traffic situation?

An officer can indicate they are in command of a traffic situation by starting and stopping traffic, which is the correct answer. This action clearly communicates to drivers when to proceed and when to halt, establishing control over the traffic flow in that area. It allows for the safe and efficient management of vehicles, especially in high-stress or complicated scenarios such as accidents or road work.

Using a whistle, waving at drivers, or directing traffic with a flashlight, while they may help in signaling or gaining attention, do not provide the same level of authority and clarity that formally controlling the flow of traffic does. These methods might not effectively communicate the need for vehicles to stop or go and could lead to confusion among drivers. Therefore, starting and stopping traffic is the most direct and recognized way for an officer to assert their command over the situation.