Positive train control (PTC) is a family of automatic train protection systems deployed in the United States.[1] Most of the United States' national rail network mileage has a form of PTC. These systems are generally designed to check that trains are moving safely and to stop them when they are not.[2]
Positive train control restricts the train movement to an explicit allowance; movement is halted upon invalidation. A train operating under PTC receives a movement authority containing information about its location and where it is allowed to safely travel. PTC was installed and operational on 100% of the statutory-required trackage by December 29, 2020.[3]