Name the method used to communicate between train crews and dispatchers.

The method used to communicate between train crews and dispatchers is radio communication. This system allows for immediate and clear exchanges of information, which is crucial for ensuring safety and efficiency in train operations. Radio communication facilitates real-time dialogue that can include updates on train status, track conditions, and any issues that may arise during a journey.

In contrast to other choices, hand signals and lanterns are used for visual communication primarily in situations where verbal exchange or radio contact is not possible, often in more direct, immediate settings like close proximity to the train. Telegraph systems are largely outdated and are not used for real-time communication in modern rail operations. Thus, radio communication stands out as the most effective and widely used method for coordinating actions and guaranteeing the safe operation of trains.