Positive train control

Positive train control (PTC) is a family of automatic train protection systems deployed in the United States. 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.

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.