The correct answer is: A. T/512.
T/512 is the authority issued to start a train from an unsignalled line. It is a written order that is issued by the train dispatcher. The order must be signed by the train dispatcher and the train crew. The order must also include the following information:
- The train number
- The destination of the train
- The time the train is to depart
- The route the train will take
- The speed limit for the train
- The location of the unsignalled line
- The name of the train crew
The train dispatcher must ensure that the train crew is familiar with the route and the speed limit before issuing the order. The train crew must also be aware of the location of the unsignalled line and the name of the train dispatcher.
The train crew must follow the instructions in the order when starting the train from the unsignalled line. The train crew must also be prepared to stop the train if necessary.
If the train crew does not follow the instructions in the order, they could be subject to disciplinary action. The train crew could also be held liable for any accidents that occur as a result of not following the instructions in the order.
The other options are incorrect because they are not the authority issued to start a train from an unsignalled line.