Which type of controlling block signals regions where no trains can enter?

The absolute block system is designed to ensure that a specific section of track cannot be occupied by more than one train at a time. This safety measure prevents collisions by clearly defining segments of the railway where no trains are allowed to enter unless the block is clear.

In an absolute block system, a signal will indicate when a block is clear or occupied. When the signal shows that the block is occupied, it effectively communicates to train operators that they should not proceed into that section. This rigid control helps maintain a safe distance between trains and is an essential feature of railway operations, particularly in busy transit systems like that of the MTA.

This system is contrasted with other types of block signaling, which might allow more flexibility or different operational structures, but do not provide the same strict assurance that no trains can enter an occupied section. Thus, the defining characteristic of the absolute block is its exclusive occupancy rule, ensuring safety by keeping blocks free of multiple trains.