More than one train may occupy the same Authority limits when operating at what speed?

The correct response focuses on the concept of restricted speed, which is a specific operational directive for trains. Restricted speed allows multiple trains to occupy the same authority limits under certain conditions. This speed ensures that a train can stop within half the distance of clear visibility, which promotes safety when trains are operating in situations where overlaps in authority may occur.

By restricting the velocity, there is an increased margin for avoiding collisions or encounters with other trains, especially when visibility or the track conditions may be compromised. It acknowledges that multiple trains can safely navigate overlapping areas without the risk associated with higher speeds, where a train may not have enough time to react to an unexpected situation.

Thus, operating at restricted speed is vital in scenarios where track authority overlaps, making it essential for safe railway operations.