What is the main purpose of a main track?

The main purpose of a main track is to serve as a track that must not be occupied without proper authority or protection. This means that only trains that have received the appropriate permissions are allowed to use this track, ensuring safety and coordination in train operations. The necessity for authority or protection helps to prevent collisions and maintain the orderly flow of train traffic, as the main track typically handles the primary movements of trains, including passenger and freight services.

The other options represent different types of tracks or usages that do not align with the fundamental function of a main track. For example, while some tracks may be designated solely for freight transport, the main track does not limit itself to just one type of service. Similarly, tracks set aside for maintenance activities or emergencies serve completely different purposes and are not classified as main tracks in a rail operation context. Therefore, the focus on authority and protection is what distinctly defines the main track and its role in railroad operations.