What is one requirement for blocking devices when using TC movements on OOS tracks?

In the context of railway operations, particularly under the NORAC (Northeast Operating Rules Advisory Committee) guidelines, the requirement for blocking devices when using Temporary Cessation (TC) movements on tracks that are out of service (OOS) is critical for ensuring safety. Blocking devices are essential as they prevent signals from being misinterpreted or acted upon when those tracks are not available for regular operations.

When blocking devices are applied to all signals, it ensures that there is a consistent and clear communication about the status of the tracks. This uniform approach helps to eliminate any confusion among train crews and dispatchers regarding which signals are active or inactive, thereby enhancing safety protocols. By ensuring that all signals are adequately blocked, the potential for accidents or unauthorized movements onto OOS tracks is significantly reduced. Thus, it becomes a fundamental requirement to maintain operational safety in such situations.

In contrast, the other options suggest either partial application of blocking devices or leaving their use to the discretion of the dispatcher, which could lead to inconsistent practices and increased risk of miscommunication on the tracks.