Which of the following statements correctly describes Rule 327?

Rule 327 is designed to provide guidance on how trains can safely enter a block under specific circumstances, particularly when operating at a restricted speed. The key aspect of this rule is that it permits train movement into a block when certain conditions are met, ensuring that safety protocols are adhered to while managing the flow of train traffic.

Restricted speed is a crucial concept here; it means the train must be prepared to stop short of any obstruction, allowing for necessary caution when entering a block that may not be fully clear. This facilitates operational flexibility while maintaining safety, especially in situations where a train may not be able to stop before reaching an obstruction.

In contrast, the other options present stricter conditions or limitations that are not representative of Rule 327. The requirement for all trains to stop before entering a block does not apply under this rule, as it allows for restricted speed entry instead. Similarly, the prohibition of any entry into blocked tracks is not accurate since Rule 327 provides conditions for safe entry. Lastly, the statement about yard limits pertains to different operational protocols that are not covered by Rule 327. Therefore, the description of allowing a train to enter a block at restricted speed aligns perfectly with the intent and specifics of Rule 327.