What information should be included in a transmission regarding train speed?

Including current speed and any changes to speed limits in a transmission is vital for several reasons. First, knowing the current speed allows all parties involved—such as train operators, dispatchers, and control centers—to maintain situational awareness. This ensures that any necessary safety measures can be taken promptly if speeds exceed safe limits.

Furthermore, communicating changes to speed limits is essential for maintaining compliance with operational protocols and safety regulations. Speed limits can vary based on track conditions, weather, and other factors, so it's important to relay any alterations to ongoing operations. This information helps prevent potential accidents and ensures that the train operates within safe parameters.

The other options lack comprehensive coverage of the essential data required for effective communication. Simply stating the maximum speed does not provide situational context and could jeopardize safety. Focusing only on speed during emergencies neglects routine operations that require constant monitoring. Lastly, providing speed limits for all trains in the area might overwhelm the communication line without offering the immediate and relevant details needed for a specific train's operation.