When is ITD not allowed to be used?

The correct answer highlights a critical safety consideration in the context of roadway worker protection. The use of ITD, or a specific type of safety equipment or protocol, is prohibited during work inside interlockings and when power tools are being used due to the heightened risks involved in these scenarios.

Interlockings are critical control systems that manage train movements at junctions, and working within them requires a high level of caution and coordination. The operation of power tools adds further complexity and potential hazards, as their use can create noise that masks auditory warnings, increase the likelihood of accidents, and complicate communication among workers. Implementing ITD in such an environment could lead to a misunderstanding of safety protocols and ultimately endanger the workers.

Other contexts mentioned in the choices, such as routine inspections or nighttime work on empty tracks, do not present the same level of risk concerning operational control systems and the potential distractions from tools. Minor repairs on non-adjacent tracks also do not inherently carry the same safety concerns that necessitate the prohibition of ITD usage.