What is the primary function of a bank home signal?

The primary function of a bank home signal is to control train movements into and out of a yard. This signal is crucial for coordinating the safe and efficient operation of trains entering or exiting railway yards, which are areas where trains can be stored, assembled, or otherwise serviced. By managing these movements, the bank home signal helps prevent accidents that could occur if multiple trains were to enter the yard simultaneously or if a train were to enter a yard while another was departing.

While the other options refer to important aspects of railway operation, they do not specifically pertain to the unique role of the bank home signal. For instance, indicating speed limits or showing the status of track switches are functions served by different types of signals within the rail system. Maintenance instructions are typically communicated through other means and are not the function of any signaling mechanism. Thus, focusing on the coordination of train movements defines the primary role of the bank home signal effectively.