Final answer:
Express trains normally only make express stops unless instructed otherwise, with the exception likely related to special circumstances affecting train service.
Step-by-step explanation:
According to the policy described, express trains running on local tracks typically adhere to making stops only at express stop locations unless directed otherwise. The phrasing of the question implies there is an exception to this rule, although the specific exception is not provided in the question. The context likely pertains to a scenario in which the normal operations of the train service are altered, for example, due to an emergency, track work, or schedule adjustments. Creating a hypothetical exception, it could be that express trains must make all local stops if there is an issue with the tracks that prevents local trains from running, thereby requiring express trains to provide broader service to ensure passengers can reach their destinations.