What is the primary role of data read from wayside transponders for ATC-equipped trains?

The primary role of data read from wayside transponders for ATC-equipped trains is to provide train localization. Wayside transponders are strategically placed along the tracks and communicate with the train's onboard systems, offering critical information regarding the train's position. This data allows for precise tracking of the train's location along the route, which is essential for safe operations.

Train localization is crucial for the Automatic Train Control (ATC) system because it enables the train to determine its exact position on the track, which in turn facilitates the effective management of speed regulation, route adherence, and overall train movements. Accurate localization ensures that trains can operate safely and efficiently, preventing collisions and enabling timely adjustments to their operation based on the current track conditions and surrounding environment.