In what situation can maintenance work on a siding commence without prior approval?

Maintenance work on a siding can commence without prior approval specifically in the case of an emergency. Emergencies often require immediate action to ensure safety and to address unforeseen situations that could pose a risk to operations, personnel, or infrastructure. This allows maintenance crews to act swiftly to resolve critical issues without the delay of obtaining prior approval, which is essential for maintaining operational safety and integrity.

In contrast, the other scenarios do not warrant the same immediate response. Daylight hours may provide better visibility, but they do not inherently necessitate bypassing the approval process. Having no trains scheduled might seem conducive to starting work, but those plans often require prior approval to ensure all protocols and safety measures are observed. Scheduled maintenance outages usually come with a pre-arranged plan, including necessary approvals in place to conduct the work systematically.