What must trains do when operating under overlapping limits?

When operating under overlapping limits, trains are required to operate at restricted speed and must be authorized by the track warrant. This procedure is essential for ensuring safety when trains are in an area where different sets of rules or authorities apply, helping to avoid collisions and ensuring that all operations are conducted under clear instructions.

Operating at restricted speed allows the train crew to maintain control of the train while navigating through potentially confusing or hazardous areas, and it ensures that the train can stop within the range of its vision or within a distance that is safe for the conditions ahead. Additionally, having a track warrant provides formal authority for the train to proceed, ensuring that all operators are informed of their rights and responsibilities in that specific segment of the track.

The other options do not align with established safety protocols for overlapping limits. Relocating to another track immediately is not necessarily required; signals must be heeded rather than ignored; and while communication is important, it is not the primary requirement in this case. The emphasis is on speed restrictions and the need for formal authorization.