Beyond Full Implementation: Next Steps in Positive Train Control

​​In this report, we examine current positive train control (PTC) and PTC-related technologies and regulations. The report includes work already performed across existing NTSB accident investigations, additional information from interviews, and public sources to provide a clear, accurate representation of the current state of PTC. The report considers PTC's capabilities, limitations, safety goals, and safety performance. The report provides analysis of safety issues impacting four areas: restricted speed operations, end-of-track collisions, switching mode, and work zone protection on active tracks. The report notes promising but not yet mature technologies that may improve PTC's safety performance and considers the role regulations may play in expanding and realizing PTC's potential to further advance rail safety. As a result of this investigation, the NTSB has made safety recommendations to the Federal Railroad Administration.

​​At present, PTC is successful at signal enforcement, but limitations in PTC systems' access to train location information impede detection of and response to train-to-train collision threats during restricted speed operations. We found that research can support the development and implementation of PTC technologies that, by reliably identifying and locating the end of a train and communicating that information to other trains, can prevent train-to-train collisions during restricted speed operations.

We also found that advancements in PTC and PTC-related technologies can prevent or mitigate the severity of end-of-track collisions in terminals; once these technologies are deployed, exceptions to PTC installation for terminals would no longer be needed. Further, we found that PTC software components for switching, or restricted, mode that require human intervention to return to active PTC protection on main tracks can result in PTC signal enforcement being unnecessarily disabled within 5 miles of the switching operation. 

Finally, we found that other technologies, such as tablet computers used by roadway workers in charge, can be deployed in PTC to improve communication and enforcement of working limits.

​​As a result of this investigation, we recommended that the FRA complete and publish research on PTC technologies to prevent train-to-train collisions during restricted speed operations and develop a plan to implement research results. We also recommended that the FRA work with railroads to eliminate exceptions to PTC installation for terminals.

We made a recommendation to the FRA to require railroads to adopt engineering controls that automatically return PTC to active mode following switching operations. This recommendation supersedes safety recommendation R-20-18 regarding engineering controls limiting the use of PTC in restricted mode on main tracks. We further recommended that the FRA require railroads to implement technologies that eliminate the risk of miscommunication about established working limits and PTC protection.