What must be done with speed restriction signs prior to a permanent speed restriction?

The correct answer involves placing speed restriction signs in advance of the restriction. This practice is essential to ensure that train crews are adequately informed of the upcoming change in speed limits before they reach the restricted section of track. By doing so, it allows them sufficient time to adjust their speed in a safe manner, minimizing risks associated with abrupt changes in speed that could lead to unsafe conditions.

Timing is crucial in maintaining the safety and efficiency of railway operations, so the advance placement of these signs is a standard protocol. This ensures that all train operators have clear and visible warnings, which is integral for proper compliance with operational procedures.

Other choices do not align with safety protocols. For instance, removing the signs as soon as a train passes could lead to confusion for subsequent trains. Placing the signs at the same time the restriction is enacted would not provide adequate warning for approaching trains, which is contrary to safety regulations. Displaying speed restriction signs only during holidays also fails to meet the ongoing need for clear communication about speed limits, which is meant to be consistent regardless of any specific dates.