What action must a tower operator take when there is an obstruction on the track?

When there is an obstruction on the track, the appropriate action for a tower operator is to notify the Railroad Control Center (RCC) and display a red signal. By notifying the RCC, the operator ensures that the situation is escalated to the appropriate personnel who can take further necessary actions, such as halting train movements in that area. Displaying a red signal serves as a visual warning to all train operators of the danger ahead, thereby preventing any potential accidents. This combination of communication and signaling is critical for maintaining safety on the rail network, as it alerts trains to stop before they reach the obstruction, allowing for appropriate measures to be taken to clear the track or address the obstruction in another safe manner.