If the gage on class 4 track is measured at 57" and there's an observed gap and plate movement, what is the initial action?

Imposing a speed restriction until compliance is achieved is the correct action in this scenario due to the observed gap and plate movement on class 4 track. This type of track requires specific conditions to ensure safe train operations, and any deviations can compromise safety.

When measuring the gage at 57 inches, and noting issues such as gaps and movement, it indicates potential instability that could lead to derailments or other safety incidents if trains operate at normal speeds. Thus, implementing a speed restriction is a prudent measure to help prevent accidents and allow for timely assessment and corrective actions to be taken.

Continuing operations as normal disregards the safety concerns associated with the observed track conditions. Notifying the Federal Railroad Administration is a necessary procedure for regulatory compliance but does not provide immediate safety measures. Initiating a track class upgrade is a longer-term solution that would not address the immediate risks present. Hence, imposing a speed restriction is the most appropriate initial action in this context to ensure the safety of rail operations.