What must a Dispatcher do before permitting opposite movement to assist a disabled train?

The reasoning behind the correct answer revolves around safety and operational protocols specific to assisting disabled trains. Issuing Form D line 8 to the disabled train is essential because it formally authorizes the movement and provides critical instructions relevant to that specific situation. Form D is typically used for communication between dispatchers and train crews, ensuring that everyone involved has a clear understanding of the orders and limitations regarding the movement.

By issuing this form, the dispatcher outlines the conditions under which the train may proceed, ensuring that the movement is safe and coordinated with the overall traffic plan in place. This procedure helps prevent conflicts or accidents that could arise if opposite movements were allowed without proper authorization and communication.

In contrast, while notifying adjacent traffic, contacting the train crew for verification, or canceling jobs might also be part of the overall safety protocols, they do not specifically address the requirements for authorizing the actual movement of the disabled train. Therefore, issuing Form D line 8 is the primary action the dispatcher must take to ensure safe and effective assistance to a disabled train.