What speed should trains exceeding Medium Speed do upon seeing an Approach Restricting signal?

When trains exceed Medium Speed and encounter an Approach Restricting signal, the appropriate action is to reduce to Restricted Speed immediately. This is necessary because an Approach Restricting signal indicates that the train is approaching a block where the signal ahead is less favorable, often signaling a need to prepare for a stop or a significant reduction in speed.

By reducing to Restricted Speed, the train can ensure it has adequate time and distance to react appropriately to the upcoming signal. Restricted Speed allows the train to proceed with caution, but at a manageable pace, so the crew can assess the track conditions and any potential obstacles. Following this protocol enhances safety, ensuring that all operational standards are met while allowing the crew to maintain control over the train's speed in preparation for the next signal indication.

The other options do not align with safe operating procedures under these circumstances. Continuing at the current speed could lead to unsafe conditions if the next signal requires a stop. Stopping at the next block may not be necessary unless indicated by the signal, and simply proceeding with caution without reducing speed does not adhere to established safety practices, which prioritize reducing speed in response to restrictive signals.