What is the rule regarding the omission of warning signs and channelizing devices during flagging?

The correct answer addresses the requirement related to flagging operations, emphasizing the importance of safety in construction and maintenance zones. When the work space is behind a barrier, it is considered adequately protected from traffic, thus minimizing the need for additional warning signs and channelizing devices. This situation allows for a safer environment for both workers and drivers, as barriers effectively separate the work zone from live traffic, reducing potential hazards.

In contrast, other scenarios listed would present risks that necessitate the use of warning signs and channelizing devices to alert drivers of the work zone and direct traffic accordingly. For example, when the work space is very close to the roadway or not sufficiently shielded by barriers, the need for additional safety measures becomes critical to prevent accidents and ensure safety for both flaggers and motorists.