Which of the following is a scenario that necessitates moving at restricted speed?

Moving at restricted speed is required when a train enters a block where there are no governing signals present. This is because the absence of signals indicates that the train cannot be sure of the conditions ahead, such as obstructions or other trains. By operating at restricted speed, the crew can react appropriately to any hazards, ensuring they can stop within half the range of vision. This practice helps maintain safety and operational integrity on the railway.

In contrast, having a clear track ahead does not necessitate restricted speed, as this typically allows for normal operating speeds unless specific conditions dictate otherwise. Restricted speed is not specifically associated with night operations alone, as it applies in various situations regardless of the time of day. Finally, while approaching a final destination may involve reduced speeds for safe stopping, it does not inherently require restricted speed unless specific obstacles or signals indicate the need for caution. Thus, the first scenario aptly defines the necessity for this operating procedure.