Positive Train Control Systems Positive Train Control is required on all U.S.A. rail systems that carry passengers or hazardous freight or both.  The idea is that if the train is out of control, and in immediate danger of a crash, the braking system will take over automatically and bring the train to a safe stop.  The U.S.A. Department of Transportation in 2015 modified the then existing laws to allow trains track that are not carrying 'toxic' goods or passengers to be exempt from the prior ruling. The BorderTransportationSystem will contain positive train control as a matter of design since it is an AI system, {Artificial Intelligence} that can self-regulate speed, braking, interval distance, and emergency actions.  Index of ... Cisco Positive Train Control: Enhancing End-to-End Rail Safety LILEE Systems - Positive Train Control solution Positive Train Control Positive Train Control (PTC) Legislation & Regulations