Which term describes an area with defined limits where only one train may operate at a time under block signaling?

• A. Absolute Block
• B. Block
• C. Coupler
• D. Consist

Answer: (A)

The situation tested is the strict one-train-per-defined-section rule used in block signaling. In railway signaling, a block is a designated piece of track with defined limits. The term that describes a block operated under a strictly exclusive occupancy rule—where only one train may be in that block at a time and entry is controlled by signals and train detection—is Absolute Block. This system ensures no second train can enter the block until the first train has fully cleared and the signal authority has been updated, providing clear, rigid separation between trains.

A general “block” describes the concept of dividing track into sections for signaling, but it doesn’t specify the strict one-train-at-a-time rule or the specific protections used to enforce it. A coupler is just the device that connects rail cars, and a consist is the arrangement of cars forming a train, neither of which relate to the occupancy-control concept described here.