If a block signal requires restricted speed due to yard limits, what must the movement be at that signal?

When a block signal indicates that a movement must be made at restricted speed due to yard limits, it is essential for the safety and operational integrity of train movements in areas where additional caution is necessary. Restricted speed means that a train must be capable of stopping within half the range of sight, which is critical in yard limits where there may be other trains, work crews, or equipment present.

By requiring the movement to be at restricted speed immediately, it ensures that the train is operated carefully and can react quickly to any unexpected situations, such as encountering a stopped train, a switch that may be set improperly, or workers on the tracks. This is a fundamental safety protocol in rail operations, particularly in areas with high potential for conflicting rail activities.

In contrast, the other options provide conditions that could lead to unsafe situations. Normal speed might not allow a train to stop in time if there’s an unexpected hazard ahead, while approach speed and high speed do not align with the necessary caution required in yard limits. Thus, the requirement to be at restricted speed immediately reflects the need for heightened vigilance in these critical areas.