What key requirement must be fulfilled before the Dispatcher permits an opposing movement against traffic in Rule 251 territory?

The correct answer focuses on the stipulation that a Form D line 8 must be issued to the disabled train before permitting an opposing movement against traffic in Rule 251 territory. This requirement is crucial because it provides a formalized and documented authority for the movements that are taking place, ensuring that all involved parties are aware of the conditions and that safety measures are in place. Issuing this form helps to maintain the integrity of communication and coordination between the Dispatcher and the crew of the disabled train.

Without this formal acknowledgment and instruction, there is a risk of misunderstandings or miscommunications that can lead to dangerous situations. The issuance of Form D line 8 signifies that both the Dispatcher and the crew are aware of the specific circumstances surrounding the movement and are taking the necessary precautions to ensure that it can proceed safely. In Rule 251 territory, where there is only one track in each direction, this careful attention to protocol becomes even more critical to prevent accidents during opposing movements.