Who are the only persons allowed to ride on engines without written authority?

The correct answer highlights that Transportation Department Supervisors and crew members are the only individuals permitted to ride on engines without requiring written authority. This is rooted in the operational protocols designed to ensure safety and accountability within the train operations.

Members of the Transportation Department are responsible for managing and overseeing various aspects of train operations, including ensuring that crews adhere to safety regulations. Their presence on the engine is often necessary for operational reasons, like supervising the crew, inspecting the engine, or other tasks directly related to the operation of the train.

Crew members also have duties that may necessitate their presence on the engine while performing official responsibilities. Allowing these individuals to ride the engine without written authority ensures that train operations can continue efficiently, with the necessary oversight for safety and compliance in place.

Other options do not align with the established safety protocols outlined in operating rule books. For instance, allowing passengers or freight workers to ride on engines would pose significant risks, as they may not be trained in the specific safety procedures necessary for such environments. Additionally, restricting the presence on engines to only maintenance staff or a single train conductor would not provide the operational flexibility needed by the Transportation Department to manage the logistics and safety of train operations effectively.