How should controlled signals be displayed before train movements?

The correct choice focuses on the importance of controlled signals in train operations, emphasizing that these signals must be displayed in a way that avoids providing unnecessary restrictive indications. This is crucial for maintaining the efficiency and safety of train movements. When signals display restrictive indications without cause, it can lead to confusion, delays, and unnecessary caution among train crews that may not be warranted by the current situation on the tracks.

In train dispatching, it is essential to provide clear and accurate indications that reflect the actual conditions ahead. This allows engineers to make informed decisions and operate trains safely without excessive restrictions that could impede their progress or cause operational inefficiencies. The intent is to strike a balance where signals convey critical information without overwhelming train crews with unnecessary restrictions that do not reflect the real-time status of the train's path.

The other options, while related to aspects of train operations, do not directly address the fundamental purpose of controlled signals in this context. They touch on various elements of communication and scheduling but do not specifically highlight the necessity of displaying signals in a manner that prevents confusion regarding restrictions.