Which system is a transponder and data-radio based train-control system which will automatically apply the brakes of an equipped train if, while approaching a Speed Restriction or Positive Train Stop Location, the speed of the train exceeds the predetermined rate?

• A. Marker
• B. Advanced Civil Speed Enforcement System (ACSES)
• C. Interlocking Signals
• D. Foul Time

Answer: (B)

This describes the Advanced Civil Speed Enforcement System. It uses a trackside transponder and two-way data-radio communications to the train’s onboard computer. As the train approaches a Speed Restriction or a Positive Train Stop location, the onboard system knows the permitted speed for that segment. If the train would exceed that limit, the system automatically applies the brakes to bring the train back within the allowed speed, even if the engineer hasn’t manually brake-tested yet. This automatic enforcement is the key feature that distinguishes ACSES from other systems.

Markers are simple location indicators along the track and don’t enforce speed. Interlocking signals manage routing and prevent conflicting movements but don’t automatically brake a train for a speed violation. Foul Time is a timetable-based rule to prevent occupancy conflicts, not an automatic braking system.