By Kim Smiley
A fire in a DC Metro tunnel early on March 14, 2016 caused delays on three subway lines and significant disruption to both the morning and evening commutes. There were no injuries, but the similarities between this incident and the deadly smoke incident on January 12, 2015 (see our previous blog on this incident) led officials to order a 24-hour shutdown of the entire Metro system for inspections and repairs.
The investigation into the Metro fire is still ongoing, but the information that is known can be used to build an initial Cause Map. A Cause Map is built by asking “why” questions and visually laying out all the causes that contributed to an incident. Cause Mapping an issue can identify areas where it may be useful to dig into more detail to fully understand a problem and can help develop effective solutions.
So why was there a fire in the Metro tunnel? Investigators have not released details about the exact cause, but have stated that the fire was caused by issues with a jumper cable. Jumper cables are used in the Metro system to bridge gaps in the third rail, essentially functioning as extension cords. The Metro system uses gaps in the third rail to create safer entry and exit spaces for both workers and passengers because of the potential danger of contact with the electrified third rail. The third rail carries 750 volts of electricity used to power Metro trains and could cause serious injury or even death if accidently touched.
The jumper cables also carry high voltage and fires and/or smoke can occur if one malfunctions. Investigators have not confirmed the exact issue that lead to this fire, but insulation failures have been identified in other locations and is a possible cause of the fire. (Possible causes can be added to the Cause Map with a “?” to indicate that more evidence is needed.)
One of the things that is always important to consider when investigating an incident is the frequency of occurrence of similar issues. The scope of the investigation and possible solutions considered will likely be different if it was the 20th time an incident has occurred rather than the first. In this case, the fire was similar to another incident in January 2015 that caused a passenger death. Having a second incident occur so soon after the first naturally raised questions about whether there were more unidentified issues with jumper cables. The Metro system uses approximately 600 jumper cables and all were inspected during the day-long shutdown. Twenty-six issues were identified and repaired. Three locations had damage severe enough that Metro would have immediately stopped running trains through them if the extent of the damage had been known.
The General Manger of the DC Metro system, Paul J. Wiedefeld, is relatively new to his position and has been both praised and criticized for the shutdown. Trying to implement solutions and reduce risk is always a balancing act between costs and benefits. Was the cost of a full-day shutdown and inspections of all jumper cables worth the benefit of knowing that the cable jumpers have all been inspected and repaired? At the end of the day, it’s a judgement call, but I personally would be more comfortable riding the Metro with my children now.
By Kim Smiley
On September 30, 2015, the National Transportation Safety Board (NTSB) issued urgent safety recommendations calling for the Federal Railroad Administration to take over the task of overseeing the Washington, DC Metro system. The NTSB has determined that the body presently charged with overseeing it (the Tri-State Oversight Committee) doesn’t provide adequate independent safety oversight. Specifically, the Tri-State Oversight Committee doesn’t have the regulatory power to issue orders or levy fines and lacks enforcement authority.
The recommendations resulted from findings from the ongoing investigation into a smoke and electrical arcing accident in a Metro tunnel that killed one passenger and sent 86 others to the hospital. (To learn more, read our previous blog “Passengers trapped in smoke-filled metro train”.) The severity of damage done to the components involved in the arcing incident have made it difficult to identify exactly what caused the arcing to occur, but the investigation uncovered problems with other electrical connections in the system that could potentially lead to similar issues if not fixed.
Investigators found that some electrical connections are at risk of short circuiting because moisture and contaminants may get into them because they were improperly constructed and/or installed. The issues with the electrical components were not identified prior to this investigation which raises more questions about the Metro’s inspection and maintenance programs. Although the final report on the incident has not been completed, the NTSB issued recommendations in June to address these electrical short circuit hazards because they required “immediate action” to ensure safety.
Investigators have found other issues with the aging DC Metro system such as leaks allowing significant water into the tunnels, issues with inadequate ventilation and questions about the adequacy of staff training. The final report into the deadly arcing incident will include recommendations that go far beyond fixing one electrical issue on one run of track.
This example is a great illustration of how digging into the details of one specific problem will often reveal information about how to improve reliability across an organization. It may seem overwhelming to tackle organization-wide improvements, but often the best way to start is with an investigation into one issue and digging down into the details.
By Kim Smiley
A standard commute quickly turned into a terrifying ordeal for passengers on a metro train in Washington, DC the afternoon of January 12, 2015. Shortly after leaving a station, the train abruptly stopped and then quickly filled with thick smoke. One passenger died as a result of the incident and 84 more were treated for injuries, predominantly smoke inhalation.
This incident can be analyzed by building a Cause Map, a visual root cause analysis. A Cause Map visually lays out the cause-and-effect relationships to show all the causes that contributed to an issue. The first step in the Cause Mapping process is to define the problem by filling in an Outline with the basic background information as well as documenting how the issue impacts the overall goals. For this example, the safety goal is clearly impacted by the passenger death and injuries. A number of other goals should also be considered such as the schedule goal which was impacted by significant metro delays. (To view an Outline and initial Cause Map for this issue, click on “Download PDF” above.)
So why were passengers injured and killed? Passengers were trapped on the train and it filled with smoke. It is unclear why the train wasn’t able to back up to the nearby station once the smoke formed and investigators are working to learn more. (Open issues can be documented on the Cause Map with a question mark to indicate that more evidence is needed.) There are also questions about the time emergency workers took to reach the train to aid in evacuation of passengers so this is another area that will require more information to fully understand. By some account, it took 40 minutes for firefighters to reach the trapped passengers.
Initial reports are that smoke was caused by an electrical arcing event, likely from the cables supporting the high voltage third rail used to power the trains. The specifics of what caused the arc are being investigated by the National Transportation Safety Board and will be released when the investigation is concluded. What is known is that there was significant smoke caused by the arc, but no fire. There have also been reports of water near the rails that may have been a factor in the arcing.
Eyewitness accounts of this incident are horrifying. People had little information and didn’t know whether there was fire nearby at first. They were told to remain on the train and await rescue, but the rescue took some time, which surely felt longer to the scared passengers. It won’t be clear what solutions need to be implemented to prevent similar problems in the future until the investigation is complete, but I think we can agree that metro officials need to work to ensure passenger safety going forward.