Which feature is crucial for the design of drums used in traffic control?

The crucial feature for the design of drums used in traffic control is the closed tops. This design is important for several reasons. Closed tops help to ensure that the drums can stack securely, which is essential for efficient storage and transport. Additionally, a closed top prevents debris from entering the drum, which could compromise its stability or effectiveness in directing traffic.

Moreover, the closed top design enhances the durability of the drum by protecting it from environmental factors. For example, rainwater can accumulate in an open-top drum, leading to issues such as rust or the formation of hazardous conditions around the work zone.

While characteristics like heavy weight, high height, and bright colors may contribute to the visibility and stability of the traffic control system, they do not offer the same functional benefits as a closed top, especially concerning safety and handling during transportation and use.