Positive Train Control

The result of 50 years of NTSB investigations and advocacy

Overview of the Issue

Positive Train Control (PTC) was on the NTSB’s Most Wanted List in some form almost every year since 2001 and was finally removed in the 2021-22 iteration of the list in light of the final rail line implementing Positive Train Control technology in 2020. The NTSB has advocated for PTC technology since 1970, following the Darien, CT train collision. The conductor of the N-48 train missed, ignored, or misinterpreted a signal to stop and enter a siding to allow the N-49 passenger train to pass. The collision resulted in the deaths of the engineer of the N-48 train and one passenger and 45 injuries. The process through which PTC technology was implemented in all railroad systems is representative of the NTSB’s role in pushing forward safety recommendations. The NTSB noticed a trend in railroad accidents where PTC technology could have prevented collisions or derailments, amplified the issue by promoting PTC technology to its Most Wanted List, advocated for the implementation of PTC technology, and supported the legislative process for the Railroad Safety Enhancement Act of 2008. 

According to the NTSB, as of January 14, 2021, it had investigated 154 PTC-preventable accidents. In those 154 preventable accidents, there were 6,883 injuries and 305 lives lost, and the NTSB issued 82 safety recommendations. PTC is a system of sensors installed in both the trains themselves and rail checkpoints that communicate with computers to automatically apply train brakes or slow down the train in cases when the engineer misses the cue to brake or slow down. 

Summary of the Incident–2008 Chatsworth Train Collision

On September 12, 2008, westbound Southern California Regional Rail Authority Metrolink train 111 collided head-on with eastbound Union Pacific Railroad freight train LOF65-12 near Chatsworth, California, causing the locomotive and first passenger car of the Metrolink train and 10 of the 17 freight cars of the Union Pacific train to derail. The impact caused the locomotive of the Metrolink train to telescope into the lead passenger car. The accident resulted in 25 fatalities, 102 injured passengers, and more than $12 million in damages. 

Prior to the collision, the westbound Metrolink passenger train and the eastbound Union Pacific freight train were traveling along the same single track. The dispatcher set the switches so that the eastbound Union Pacific freight train would enter a siding, which would allow the westbound Metrolink passenger train to continue on the main track. The alignment of the switches triggered a red signal to instruct the engineer of the Metrolink passenger train to stop until the Union Pacific freight train had safely entered the siding. Once the Union Pacific train was off the main track, the signal would change to give the engineer of the Metrolink passenger train clearance to continue along the main track. The preceding signals would have flashed yellow, alerting the Metrolink engineer of the upcoming red signal. Under Metrolink rules, the engineer radios the signal to the conductor, and, if the signal is anything other than all clear, the conductor must repeat back the signal. Metrolink’s operations center recorded the engineer noting the flashing yellow signal, but the conductor told investigators he did not remember hearing the engineer calling out the yellow signal. Records show that neither the engineer nor the conductor called out the following solid yellow signal, which signalled that the following signal would be red and require a full stop. The Union Pacfic freight train had been exiting a tunnel and entering a curve when the crew saw the Metrolink passenger train ahead. The crew applied the emergency brakes but were unable to prevent the collision.

NTSB Investigation

The NTSB was notified at 7:45pm on the day of the accident and deployed members from the Washington, D.C. headquarters and the Chicago, Illinois; Gardena, California; and Jacksonville, Florida field offices. The Board Member on scene was Kathryn O’Leary Higgins. The FRA, Metrolink, Connex Railroad, LLC, Union Pacific Railroad, California Public Utilities Commission, Brotherhood of Locomotive Engineers and Trainmen, United Transportation Union, Los Angeles Police Department, Los Angeles Fire and Rescue, Bombardier Transportation Corporation, and Mass Electric Construction Company were parties to the investigation. 

Board concluded that the probable cause of the accident was the Metrolink train engineer’s missing the red signal because he was texting while operating the train, and that the lack of PTC equipment contributed to the crash. Although there was no recording of the signal, investigators were able to conclude that the signal was indeed red and the engineer should have brought the train to a stop ahead of the switch that would have sent the Union Pacific train to the siding. The report also notes evidence that the Metrolink engineer potentially had a sleep apnea disorder. However, the Board did not believe that the condition played a factor in the engineer’s performance, as all signs pointed to the engineer being awake and alert at the time of the collision. 

The Board adopted the final report on January 21, 2010. The NTSB recommended that the FRA require the installation of inward and outward facing audio and visual recording equipment and require that railroads regularly evaluate the recordings to ensure that crews are abiding by all rules and regulations.

Policy Changes

The Chatsworth train collision pushed Congress to pass the Railroad Safety Enhancement Act of 2008. The bill required railroads to implement PTC systems by December 31, 2015. The Surface Transportation Extension Act of 2015 extended the deadline for PTC implementation to December 31, 2018. If a railroad would not meet the 2018 deadline, they were required to submit a request to the FRA for an extension and provide a schedule for implementation of the technology. 

In 2021, the NTSB celebrated the full implementation of PTC systems in railroads across the country and the 2021-2022 Most Wanted List did not include Positive Train Control.