What conditions must be met for certain work crews to operate without Form D line 4?

For work crews to operate without Form D line 4, the requirement that the work is conducted on interlocking limits without disturbance to the track is key. In this context, interlocking limits represent an area where signals and track switches are controlled to ensure safe train operations. When work is performed within these limits and does not interfere with the normal usage of the track or the passage of trains, it demonstrates that safety protocols are in place and that risks are minimized.

This condition allows crews to perform necessary tasks without the additional administrative step of filing a Form D line 4, which is typically required to ensure that all relevant parties are aware of the work being done and the potential implications for train movements. Adhering to this requirement helps maintain operational efficiency while upholding safety standards, as it prevents any miscommunication that could lead to dangerous situations.

Other situations proposed, such as needing permission from the dispatcher, stipulating crew experience or mandating breaks for other workers, do not inherently address the operational safety context of working within interlocking limits while ensuring no disruptions to train activity occur. Thus, the correct answer aligns directly with the need to ensure that the work being done is appropriate for operating without the additional requirement of the Form D line 4.