This term refers to a combination of technologies that together stop a train before certain accidents occur, specifically preventing train-to-train collisions; derailments caused by excessive speed; unauthorized incursions by trains onto sections of track where maintenance activities are taking place; and the movement of a train through a track switch left in the wrong position.
A PTC system consists of three main elements:
The Rail Safety Improvement Act of 2008 calls for passenger railroads and freight railroads to install PTC on mainlines used to transport passengers or toxic-by-inhalation (TIH) materials. There are some exceptions provided for in the Act.
The Rail Safety Improvement Act of 2008 originally called for passenger railroads and Class I freight railroads to install PTC by the end of 2015 on mainlines used to transport passengers or toxic-by-inhalation (TIH) materials. In October 2015, the statutory deadline for PTC installation was extended to the end of 2018, with further extensions available up to the end of 2020 to allow time for railroads to adequately test their systems.
Short lines are required to install PTC by the end of 2020. Some short lines will install earlier at the request of the Class I interchange partners (known as Host Railroads in PTC parlance).