Which of the following best describes a block limit?

A block limit refers to a specific section of railroad track that is governed from a safety and operational standpoint, where trains are prohibited from proceeding unless they have the proper authorization. This concept is fundamental to maintaining train operations and ensuring safety on the railways. Block limits are established primarily to prevent collisions and manage train movement within designated areas of track, especially in busy systems like the MTA. When trains enter a block limit, they must have signals or commands that indicate they are permitted to proceed; otherwise, they must stop until authorized.

Understanding this definition highlights the importance of maintaining safe distances between trains and managing traffic effectively on the railways. The other options do not accurately define a block limit: maintenance areas pertain to service and repairs, temporary stops focus on passenger operations rather than safety protocols, and fixed schedules pertain to timetable management rather than the operational safety represented by block limits.