Which circuit breakers should cut out if the PA4 train is bucking?

When a train experiences bucking, which typically refers to a rapid back-and-forth movement that can lead to instability and potential derailment, the proper circuits that should be cut out are those associated with propulsion and braking control. Dynamic brakes help slow the train down by converting the kinetic energy into electrical energy, which can become hazardous if applied during bucking as it can exacerbate the instability.

The motor cut-out is also critical because the motors drive the train's wheels. If the train is bucking, maintaining power to the motors could worsen the situation by continuing to propel the train forward or backward erratically. Therefore, removing the dynamic brake and cutting out the motors prevents any further exacerbation of the bucking behavior, ensuring the train can come to a stable stop safely without additional forces acting on it.

This choice directly addresses the issues caused by the bucking and is aimed at restoring control and safety to the operation, which aligns with the proper protocols for managing such mechanical instability.