What are the two primary components of NORAC's block system?

• A. Signal aspects and automatic train control devices.
• B. The use of track blocks and signals to control train movements within each block.
• C. Block boundaries and interlocking switches.
• D. Crew rosters and station dispatching procedures.

Answer: (B)

The block system is built around dividing the track into defined sections, or blocks, and using signals to control movements within each block. The two primary components are the track blocks themselves and the signals that authorize entry into and movement through those blocks. Blocks establish where one authority ends and the next begins, preventing trains from entering an occupied section. Signals provide the mechanism to grant or restrict permission to proceed inside a block based on track occupancy and protection needs.

Other options mix in elements that aren’t the defining parts of NORAC’s block system. For example, while signal aspects are involved in signaling, automatic train control devices aren’t the fundamental two components of the block system. Interlocking switches relate to safe route configurations but aren’t the two core components of the block system itself. Crew rosters and station dispatch procedures aren’t part of how the block system is defined.