What are the signals used at congested stations to manage train spacing called?

The correct answer refers to the signals specifically designed to manage train spacing at congested stations. These signals, known as S.T. signals (Standby or Stop signals), are vital for maintaining safety and efficiency in areas where train traffic is heavy. They provide the necessary guidance to train operators, ensuring sufficient distance between trains to prevent collisions and allow for smooth arrivals and departures.

While the other signals mentioned may play roles in train operations, S.T. signals are distinct in their direct function of managing spacing at points where density of trains is high. Blocking signals, for instance, are used to protect segments of track and prevent trains from entering occupied blocks, but they do not specifically address spacing concerns at stations. Clearance signals provide information about the available space for a train to occupy, whereas approach signals are more about preparing the train for upcoming station activities rather than regulating spacing.