Which action could lead to crew decertification?

Speeding while on duty is a critical safety violation that can jeopardize not only the crew's safety but also the safety of all personnel and passengers involved in rail operations. Compliance with speed limits is essential for maintaining control over the train and ensuring that it can stop safely in response to signals, track conditions, or other unexpected circumstances.

Engaging in speeding signifies a lack of adherence to operational rules and can indicate broader issues related to crew discipline and situational awareness. The consequences of such actions can be severe, including potential accidents, injuries, and even fatalities. Therefore, this type of behavior would likely lead to crew decertification as it severely undermines the integrity of rail operations and the commitment to safety that is expected from all crew members.

In contrast, the other choices involve actions that are generally aligned with maintaining safety and efficiency in train operations, such as ensuring cars are clean, completing required tests, and adhering to safety protocols.