The National Transportation Safety Board (NTSB) has released the final report for its investigation of the March 2, 2024, collision and derailment of three Norfolk Southern (NS) trains near Easton, Pa. The accident, it said, underscores the importance of the Federal Railroad Association (FRA) “completing research into PTC [Positive Train Control] technologies to prevent train-to-train collisions during restricted speed operations,” and continuing work on “analyzing data that will help revise training and increase oversight to ensure that operating crews use restricted speeds correctly.”
What happened?
On March 2, 2024, about 7:11 a.m., eastbound NS intermodal train NS268H429 collided with the rear of stationary NS intermodal train NS24XH101 on main track 2 on the Allentown Road Subdivision on the Lehigh Line near Easton, (see figure above), according to the report that was issued April 10 (download below). “As a result of the first collision, train NS268H429 derailed three railcars that then fouled the adjacent main track 1,” the NTSB said. “Just over one minute later, a second collision occurred when train NS19GH501 struck the derailed equipment while traveling westbound on main track 1. As a result of the second collision, train NS19GH501 derailed six railcars and two locomotives. Three of the six derailed railcars were placarded as hazardous materials tank cars: one containing ethanol residue and two containing butane residue. The tank cars did not breach or release hazardous materials. The two derailed locomotives partially submerged in the Lehigh River and discharged locomotive diesel fuel into the water … Four crewmembers from the accident trains were transported to a local hospital, treated for minor injuries, and released.” At the time of the collisions, the NTSB noted, visibility conditions were daylight and overcast; the weather was 35°F with light rain.
“Before the accident, eastbound train NS268H429 was operating within the same signal block as eastbound train NS24XH101, which had stopped on main track 2 because of additional train traffic in the area, short of Control Point Redington (crossover) where the home signal was displaying a stop signal,” the NTSB reporrted. “Eastbound train NS268H429 operated past the automatic signal at milepost 85, where the signal was indicating for the train to proceed at restricted speed and be prepared to stop. Train NS268H429’s maximum speed was authorized by wayside signal indications and enforced by a positive train control (PTC) system.” In an interview with investigators, “the engineer said that he knew that the rear of train NS24XH101 was in the signal block that his train was entering and assumed it was continuing to move,” the NTSB said. “The train was operating in an area with limited visibility because of elevated terrain and vegetation along the curved tracks that ran on river grade and parallel to the Lehigh River, causing the train’s engineer to only be able to see train NS24XH101 for the first time when it was about eight railcar-lengths away. The train was rounding a 4° curve when it collided with the rear of train NS24XH101. Before the collision, the engineer attempted to slow the train primarily through the use of the locomotive’s dynamic and independent braking systems. However, these braking efforts did little to reduce the train’s speed in the 17 seconds leading up to the collision.”
Probable Cause
The probable cause of the multi-train collision “was the failure of the engineer of train NS268H429 to operate his train in accordance with restricted speed requirements and stop before colliding with train NS24XH101,” the NTSB determined. “Contributing to the accident were insufficient safeguards to compensate for human error, including current positive train control systems that do not prevent train-to-train collisions during restricted speed operations.”
NTSB Analysis
The collisions involved eastbound train NS26811429 striking the rear of stationary train NS24XH101, and then westbound train NS19GH501 subsequently colliding with derailed railcars from eastbound train NS26811429, which were on the tracks. “Westbound train NS19GH501 was not required to operate at restricted speed and was traveling about 22 mph, which was below the maximum authorized speed, at the time of the second collision,” the NTSB reported. “The operator of eastbound train NS268H429 failed to operate the train at restricted speed as evidenced by the fact that the train was moving at a speed faster than his ability to stop the train before colliding with stopped eastbound train NS24XH101. Although the train operator was in compliance with the upper-speed threshold defined for restricted speed by operating the train at 13 mph, he did not comply with the more restrictive requirement to operate at a speed that would allow him to stop the train within half his range of vision.”
In an interview with the NTSB, the operator of train NS268H429 indicated “he believed that train NS24XH101 was still moving and that he expected this train to have cleared the signal block they were in before his train reached Control Point Redington (the end of the signal block),” according to the agency. The operator’s statement, along with the train handling methods employed to control the train in the minutes before the collision, NTSB said, “illustrate the risks associated with human factor errors when attempting to operate at restricted speed.” According to the agency, “while crew training and operational compliance activities are currently the only safeguards railroads have to mitigate human factor risks inherent in restricted speed collisions, future enhancements to PTC could and should be developed and implemented by the railroad industry to prevent future train collisions and to mitigate the risk of human factor errors while operating trains at restricted speeds.”
The NTSB highlighted this need in its investigation of the June 5, 2018, accident between two trains in Kingman, Ariz. The agency said it recommended that the FRA “require all railroads to revise training and increase oversight to ensure that operating crews properly use restricted speeds.” Restricted speed and the challenges associated with it, were also discussed in the NTSB’s 2023 special report, Beyond Full Implementation: Next Steps in Positive Train Control, in which the agency “recommended that the FRA complete and publish current research into PTC technologies to prevent train-to-train collisions during restricted speed operations, and to develop and implement a plan based on the results of that research.” Although work is “ongoing to optimize PTC technology,” the NTSB said, “until it is operational, reliance on PTC-enforced low speeds and the crew’s adherence to restricted speed requirements remains a potential safety gap that can be mitigated only through the increased training of train crews and an effective railroad oversight plan that routinely reinforces this training. Further, while PTC is successful at signal enforcement, this [three-NS train] accident demonstrates the current limitations in PTC systems’ access to train location information, which impede the detection of and response to train-to-train collision threats during restricted speed operations. Restricted speed is not a fixed value; with variables such as the stopping distance of the train, sight distances, conditions affecting visibility, and any speed limits set by the railroad. The effectiveness of restricted speed at preventing collisions depends on the crew’s vigilance, awareness, and ability to rapidly evaluate these variables, which can be unreliable.”
According to the NTSB, on the day after the accident (March 3, 2024) NS issued a “serious incident notice to its employees elevating awareness to the rules associated with restricted speed,” and the FRA released a safety advisory “emphasizing the importance of complying with railroad operating rules when a train is operating at restricted speed.”
