Positive Train Control (PTC) systems can eliminate the consequences of collision or derailment. However, prior to the full-scale deployment of these systems, the Federal Government must conduct a regulatory review and approve the risk analysis of the PTC system performance. The objective of this review is to ensure that the operating environment after installation of the PTC system is at least as safe as the operating environment before the system installation. This paper is intended to provide researchers an understanding of PTC, the reason for its use, the regulatory requirements for the required comparative risk analysis of the PTC system, the critical failure modes that the comparative analysis must address, and future work that would facilitate the risk assessment process.