Tag Archives: NTSB

Root Cause Analysis - Incident Investigation

NTSB recommends increased oversight of DC Metro

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.

Root Cause Analysis - Incident Investigation

Concrete slab smashes truck killing 3

By Kim Smiley

On April 13, 2015, a large section of a concrete barrier fell from an overpass onto a truck in Bonney Lake, Washington. A couple and their baby were in the vehicle and were all killed instantly. Investigators are working to determine what caused this accident and to determine why the road under the overpass remained open to traffic while construction was being done on the overpass.

A Cause Map, a visual method of root causes analysis, can be built to help understand this accident. More information is still needed to understand the details of the accident, but an initial Cause Map can be created now to capture what is known and it can be easily expanded to include additional information as it becomes available. A Cause Map is created by asking “why” questions and visually laying out the answers to show the cause-and-effect relationships. (Click here to learn more about basics of Cause Mapping.)

In this accident, three people were killed because the vehicle they were riding in was smashed by a large slab of concrete. The vehicle was hit by the concrete slab because it was accidently dropped and the truck was under the overpass at the time it fell because the road was open to traffic. (When two causes are both needed to produce and effect, the causes are listed on vertically on the Cause Map and separated by and “and”.) The road would typically have been closed to traffic while heavy work was performed on the overpass, but the work plan for the construction project did not indicate that any heavy work would be performed on the day of the accident.   At some point the actual work schedule must have deviated from the planned schedule, but no change was made in plan for managing traffic resulting in traffic traveling under the overpass while potentially dangerous construction was performed.

Investigators are still working to understand exactly why the concrete slab fell, but early indication is that temporary metal bracing that was supporting the concrete may have failed due to buckling. The concrete barrier on the overpass were being cut into pieces at the time of the accident so that they could be removed as part of a $1.7 million construction project to improve pedestrian access which included adding sidewalks and lights.

Once the details of what causes this tragic accident are better understood, solutions can be developed and implemented that will help reduce the risk of something like this happening again. To view a high level Cause Map of this accident, click on “Download PDF” above.

You can also read a previous blog “Girder Fell on Car, Killing 3” to learn more about a similar accident that occurred in 2004.

Root Cause Analysis - Incident Investigation

Safety Concerns Raised by 5 Railroad Accidents in 11 Months

By ThinkReliability Staff

The National Transportation Safety Board investigates major railroad accidents in the United States. It was not only the severity (6 deaths and 126 injuries) but the frequency (5 accidents over 11 months) of recent accidents on a railroad that led to an “in-depth special investigation“. Part of the purpose of the special investigation was to “examine the common elements that were found in each”.

When an organization sees a recurring issue – in this case, multiple accidents requiring investigation from the same railroad, there may be value in not only investigating the incidents separately but also in a common analysis. A root cause analysis that addresses more than one incident is known as a Cumulative Cause Map, and it captures visually much of the same information in a Failure Modes and Effects Analysis, or FMEA.

The information from the individual investigations of each of these accidents can be combined into one analysis, including an outline addressing the problems and impacts to the goals from the incidents as a whole. In this case, the problems addressed include issues on the Metro-North railroad in New York and Connecticut from May 2013 to March 2014. The five incidents during that time period resulted in 4 customer deaths and 126 injuries, 2 employee deaths, and over $23.8 million in property damage.

The analysis of the individual accidents can be combined in a Cumulative Cause Map to intuitively show the cause-and-effect relationships. The customer deaths and injuries, and the property damage, resulted from train derailments and a collision. The train collision resulted from a derailment. In two of the cases, the derailment was due to track damage that had either been missed on inspection or had maintenance deferred. In the third derailment (discussed in a previous blog), the train took a curve at an excessive rate of speed due to fatigue of the engineer. Inadequate track inspections and maintenance, and deferred maintenance were highlighted as recurring safety issues to the railroad.

Both of the employee fatalities resulted from workers being struck by a train while performing track maintenance. In one case, the worker was outside the designated protected area due to an inadequate job safety briefing. In the other, a student removed the block while working unsupervised, allowing a train to travel into the protected area. The NTSB also identified inadequate safety oversight and roadway worker protection procedures as areas needing improvement. While the NTSB already released recommendations with each of the individual investigations, it plans to issue more based on the cumulative investigation addressing all five incidents. View an overview of all 5 incidents by clicking “Download PDF” above.

Root Cause Analysis - Incident Investigation

Girder Fell on Car, Killing 3

by Kim Smiley

On May 15, 2004, a girder fell off an overpass and hit a car driving on the road below, killing all three occupants of the vehicle.  The National Transportation Safety Board (NTSB) investigated the incident to determine what caused the fatal accident.  The findings from the investigation can be used to build a Cause Map, a visual root cause analysis, which illustrates the causes that contributed to the accident.

In this example, the girder hit the car because it fell from an overpass and the car was driving on the road below it.  The girder was temporarily installed on the overpass because it was being used to add two additional lanes to the overpass.  The work was being performed at night in effort to minimize the impact on the heavy traffic that normally used the roads involved.  The workers believed the girder attached to the overpass was in a safe condition so they had opened the road beneath it to traffic.

The girder fell because it was inadequately fastened to the overpass.  The NTSB determined that the girder wasn’t installed plumb to the bridge and it was inadequately bolted to the bridge which allowed the girder to twist and ultimately fall.  The investigation also determined that the girder was inadequately fastened because the project wasn’t planned well.  The original work plan called for two girders to be spliced together and then fastened to the bridge, but a delay in work meant that the subcontractor was only able to get one girder up before the work was halted to allow the roads to be opened for morning rush hour.  (Weather delays postponed the work further and the single girder was fastened to the bridge for several days prior to falling.) There were also no Professional Engineers involved in the planning and no formal drawings created of how one girder would be fastened to the bridge.

The NTSB investigation also determined that the guidance that governed bracing was inadequate.  The language used was confusing and there was a lack of consistent standards.  The oversight of the contractor’s work was also inadequate since the inspector did not notice that the girder wasn’t secured adequately.

As a result of this investigation, the NTSB made several specific suggestions to revise bracing standards to improve clarity.

To view a high level Cause Map of this incident, click “Download PDF” above.