### Question
How does SAFETY define positive train control system?


### Answer
Under *49 U.S.C. § 20157*, **positive train control system** is defined as:

> a system designed to prevent train-to-train collisions, over-speed derailments, incursions into established work zone limits, and the movement of a train through a switch left in the wrong position

#### Citation:
  - *49 U.S.C. § 20157*
  - Heading: **SUBTITLE V-RAIL PROGRAMS > PART A-SAFETY > CHAPTER 201-GENERAL > SUBCHAPTER II-PARTICULAR ASPECTS OF SAFETY**

