Collision Avoidance That Stops at the Yard Gate

Positive Train Control (PTC), the federally mandated collision avoidance system for freight and passenger railroads, achieved "full implementation" in December 2020 — yet significant safety gaps remain. PTC cannot prevent train-to-train collisions during restricted-speed operations because it lacks sufficient train-location precision. PTC can be administratively disabled ("switching mode") in terminal areas. Workers in established work zones are not protected by PTC. The NTSB has characterized the current system as a "floor, not a ceiling" and issued a special investigation report documenting these gaps.

Terminal areas and restricted-speed movements account for a significant proportion of train-to-train collisions and worker-strike incidents. Since the 1997 roadway worker protection rules, 73 rail workers have died on the job. Since 2021, the NTSB has participated in 18 investigations involving roadway worker fatalities. Each collision during restricted-speed movement or in a terminal has potential for derailment, hazmat release, and worker casualties — precisely the scenarios PTC was expected to prevent.

PTC as implemented uses GPS, wireless communication, and wayside signals to enforce speed limits, signal compliance, and work zone authority limits. However, GPS precision is insufficient for the close-proximity train separation required at restricted speeds (typically 20 mph or less, within visual range). The Norfolk Southern rear-end collision in Easton, PA (2024) illustrated this: an engineer failed to follow restricted speed requirements, but PTC could not have prevented the collision because it lacks sufficient location granularity. PTC permits administrative disabling during yard and terminal operations — no technology-based protection replaces it in these excluded zones. The current regulatory framework considers PTC "fully implemented" and does not require gap closure. FRA research on enhanced PTC capabilities for restricted-speed protection is underway but not complete.

Higher-precision train positioning (beyond GPS alone) — such as track-circuit integration, radar, or differential GPS — would enable PTC to enforce separation at restricted speeds. Eliminating administrative PTC bypass modes in terminal areas and replacing them with technology-based protections appropriate for low-speed, high-density operations would close the switching-mode gap. A regulatory framework that treats "full implementation" as a baseline rather than an endpoint would create accountability for gap closure.

A team could prototype a higher-precision train positioning system combining GPS with inertial measurement units (IMUs) and track-circuit data to achieve the meter-level accuracy needed for restricted-speed separation. Another approach: develop a simulation environment modeling PTC coverage gaps in terminal areas using real track geometry data to quantify collision risk under various enhancement scenarios. Relevant skills: positioning systems, control systems, railroad operations, or simulation modeling.