During what scenario must Engineers be especially vigilant about their certification?

Engineers must be especially vigilant about their certification when they are on duty because their responsibilities directly impact the safety and efficiency of train operations. Being on duty means they are actively engaged in tasks that require adherence to safety regulations and operational protocols. This includes ensuring they are fully licensed and trained for the equipment and circumstances they are dealing with, as their actions could affect not only their own safety but also that of passengers and crew. It's essential for Engineers to be aware of their certification status to comply with regulatory requirements and maintain operational integrity while performing their duties.

While working alone, dealing with personal issues, or being under supervision can influence an engineer's focus or performance, the critical aspect of being on duty encompasses all these situations, emphasizing the need for full awareness and compliance with certification at all times during operational activities.