What must a track car do before and after entering an interlocking?

Before and after entering an interlocking, a track car must contact the block operator. This is crucial because the block operator is responsible for ensuring that the interlocking and the associated signals are set to allow safe passage. By making contact, the track car crew communicates their intentions and verifies that the track is clear, thus maintaining safety protocols within the rail system.

In this context, communication with the block operator ensures that all relevant information about train movements and signal statuses is shared, allowing for coordinated operations within the interlocking. This step is essential for preventing accidents and facilitating smooth train operations.

The other options, while they may involve aspects of train operations, do not specifically address the critical requirement of communicating with the block operator when entering or exiting an interlocking.