What is the best course of action for a train operator who notices severe arcing fumes from a grounded shoe beam?

The best course of action in this situation is to stop the train immediately. If a train operator notices severe arcing fumes from a grounded shoe beam, it indicates a potential electrical fault which could lead to equipment failure or a fire hazard. Immediate action is crucial for safety. Stopping the train will allow the operator to assess the situation more thoroughly and determine the necessary steps to mitigate any risks associated with the electrical issue.

Though notifying the conductor may be a part of the protocol, it should follow the immediate action of stopping the train to ensure the safety of everyone on board. Continuing to coast to the next station without addressing the alarming signs of arcing could exacerbate the situation and put passengers and crew members at risk. Emergency brakes might be necessary depending on the circumstances, but they should be considered once the decision to stop the train is made. The priority must be to halt the train in a controlled manner to address the potential danger presented by the grounded shoe beam.