Under what condition are certain trains exempt from visual inspection after an emergency brake application?

The correct answer is based on the principle that visual inspections are primarily concerned with identifying any potential damage or defects that may have been caused by severe slack action during an emergency brake application. Severe slack action can lead to issues such as equipment distress or misalignment that may not be immediately visible. Therefore, if there has been no severe slack action, the likelihood of significant damage is diminished, which allows certain trains to be exempt from the requirement of a visual inspection.

This approach helps maintain operational efficiency while ensuring safety, as it avoids unnecessary delays for trains that are unlikely to have sustained any damage. The emphasis on slack action highlights an essential aspect of train operations, where the mechanics of coupling and braking play a crucial role in overall train integrity and safety.