When is it acceptable to display a Conditional Approach sign less than 1 ½ miles in advance of the working limits?

Displaying a Conditional Approach sign less than 1 ½ miles in advance of the working limits is acceptable when near terminals and yards because these areas often require different operational considerations compared to mainline tracks. In terminal and yard settings, trains are typically operating at slower speeds, and the proximity of working limits often necessitates signaling tailored to those conditions. This allows for effective communication of potential hazards and ensures that train crews are aware of any restrictions in a timely manner, promoting safety and operational efficiency. The other scenarios presented do not generally align with the established protocols for signage in rail operations, which is why they do not apply here.