Which of the following is NOT a common formation used in crowd control?

The circle formation is not commonly used in crowd control situations. This is primarily due to its structure, which can lead to a lack of clear direction and can potentially create confusion among both the crowd and the personnel managing it. The circle does not effectively funnel individuals or create a controlled environment that allows for the swift movement and response necessary in crowd management scenarios.

In contrast, formations like echelon, diamond, and wedge are specifically designed for effective crowd control. The echelon provides a staggered arrangement that allows officers to see and engage the crowd effectively while maintaining a controlled flow. The diamond formation offers a strong and visible presence, enhancing the ability to manage and disperse crowds while maintaining order. The wedge formation is particularly useful for pushing through a crowd or creating a path, allowing for rapid movement in tight situations. Each of these formations has established advantages in crowd control to help maintain safety and order.