Which statement describes an Automatic Block Signal System (ABS)?

Which statement describes an Automatic Block Signal System (ABS)?

• A. A block signal system that relies on manual operations.
• B. A system that uses only verbal signals.
• C. A block that is governed by automatic signals only.
• D. A block signal system in which the use of each block is governed by an automatic block signal, cab signal, or both.

Answer: (D)

Automatic Block Signal System means each block is controlled by signals that operate automatically in response to track occupancy and train presence. These signals guide train movement without requiring manual intervention, and many systems also use cab signals to convey the same or additional information directly to the engineer. Some installations use automatic block signals alone, while others use both automatic signals and cab signals. This combination is why the description that the use of each block is governed by an automatic block signal, cab signal, or both best fits ABS. The other statements describe setups that either rely on manual control, rely only on verbal signals, or imply automatic signals are always used without cab signaling, which isn’t as complete as the standard ABS definition.

Automatic Block Signal System means each block is controlled by signals that operate automatically in response to track occupancy and train presence. These signals guide train movement without requiring manual intervention, and many systems also use cab signals to convey the same or additional information directly to the engineer. Some installations use automatic block signals alone, while others use both automatic signals and cab signals. This combination is why the description that the use of each block is governed by an automatic block signal, cab signal, or both best fits ABS. The other statements describe setups that either rely on manual control, rely only on verbal signals, or imply automatic signals are always used without cab signaling, which isn’t as complete as the standard ABS definition.