Which system automatically applies full service brakes when speed exceeds a predetermined rate under a speed restriction?

• A. Block Signal System
• B. Speed Controlled Train
• C. Automatic Block Signal System
• D. Automatic Speed Control System

Answer: (D)

Automatic Speed Control System is designed to enforce speed limits automatically. It continuously compares the train’s actual speed with the predefined limit for the current speed restriction. If the train starts to exceed that limit, the system automatically applies the brakes to reduce speed and bring it back under the allowed rate. Once the speed is back within the limit, the system releases the brakes, allowing normal operation to continue at or below the restriction. This targeted automatic braking helps ensure compliance with speed restrictions without waiting for driver action.

The other systems are about signaling and train separation, not automatic speed enforcement, and a generic “Speed Controlled Train” doesn’t specify the automatic braking to meet a speed restriction.