When should a ticket sweep be performed?

A ticket sweep is an important procedure in the context of rail operations and revenue assurance, particularly to verify that all passengers have valid tickets. Performing a ticket sweep during a crew change or if there is suspected fraud is essential because this is a critical time when the integrity of the ticketing process might be compromised. Changes in crew can lead to lapses in oversight, and conducting a sweep ensures that all passengers have proper tickets at this transition.

When there are suspicions of fraudulent activity, a sweep becomes even more crucial, as it allows the staff to promptly identify and address any issues related to unauthorized travel and thus helps to maintain the overall efficiency and revenue integrity of the service.

While the other options may contribute to general ticketing diligence, they do not focus on specific instances where immediate verification is necessary, such as at crew changes or when fraud is suspected. This allows for timely and effective management of ticket compliance.