What type of ATC system is primarily found on freight locomotives?

The Locomotive Speed Limiter (LSL) system is essential for ensuring that freight locomotives operate safely and efficiently. This system is designed to automatically regulate the speed of the train, preventing it from exceeding predetermined limits. The LSL is particularly important in freight operation because freight trains typically have varied loads and can take longer to stop than passenger trains. By maintaining proper speeds, the LSL helps to reduce the risk of accidents due to human error or mechanical failure.

This system functions by monitoring the train's speed and intervening if the set speed limit is breached, thereby promoting compliance with safety regulations and enhancing overall operational efficiency. The focus on speed limiting reflects the nature of freight operations, where maintaining a consistent and safe speed is crucial for the safety of the crew, the cargo, and the infrastructure.

In contrast, the other options represent systems that serve different purposes. Automatic Train Control (ATC) is more general and can encompass various technologies, while Centralized Traffic Control pertains to signaling and routing rather than speed regulation. An Aspect Display Unit primarily provides visual signals for train operation rather than direct speed limiting. Thus, the LSL stands out as the specifically tailored system for managing operational speeds in freight locomotives.