Incident: Brake Disc Hub Failures in Metro Rail Cars.

Published Date: 2012-03-08

Postmortem Analysis
Timeline 1. The software failure incident involving brake parts falling from trains occurred in December [10635]. 2. Another incident involving a friction ring falling from a rail car happened on January 6 [10635]. Therefore, the software failure incidents occurred in December and January.
System unknown
Responsible Organization 1. Metro (Washington Metropolitan Area Transit Authority) - The software failure incident involving brake disc hubs on rail cars was caused by issues with the design and material of the hubs, leading to their premature failure [10635].
Impacted Organization 1. Metro - The software failure incident involving brake disc hubs impacted Metro's rail cars, specifically the 5000 series and 6000 series [10635].
Software Causes unknown
Non-software Causes 1. The failure incident was caused by brake parts, specifically the brake disc hubs, that were found to fail sooner than expected due to fatigue [10635]. 2. The design and material of the brake hubs contributed to the failure, as they were not able to withstand the operating conditions and developed cracks [10635]. 3. Lack of timely replacement of the defective parts due to financial constraints and delayed decision-making also played a role in the failure incident [10635].
Impacts 1. The software failure incident involving brake parts falling from trains in December shut down service along the downtown core of the Orange and Blue lines for hours, disrupting commuter travel [10635]. 2. The incident led to Metro pulling 16 rail cars from service to be examined for possible "hub failure," causing operational disruptions and potential delays for passengers [10635]. 3. Metro inspected 464 rail cars with similar brakes after a friction ring fell from a 2000 series rail car in January, leading to the replacement of 290 friction rings on brake assemblies showing wear, impacting maintenance schedules and resources [10635].
Preventions 1. Regular and timely replacement of the brake disc hubs in the rail cars could have prevented the software failure incident [10635]. 2. Immediate action upon discovering the issue in 2006 and not delaying the replacement of the defective parts could have prevented the incident [10635]. 3. Prioritizing safety and maintenance over financial constraints could have prevented the software failure incident [10635].
Fixes 1. Replacement of the brake disc hubs on the rail cars, with the new hubs being bigger and made of a different, stronger material [10635]. 2. Implementation of redesigned brake hubs by the manufacturer, Knorr Brake, to address the issue of hub failure due to fatigue [10635].
References 1. Metro General Manager Richard Sarles 2. Metro chief spokesman Dan Stessel 3. Deputy General Manager Dave Kubicek 4. Board member Mort Downey 5. Manufacturer Knorr Brake 6. The Washington Post

Software Taxonomy of Faults

Category Option Rationale
Recurring unknown The articles do not mention any software failure incidents related to either one_organization or multiple_organization. Therefore, the information about the software failure incident in the context of organizations or their products and services is unknown.
Phase (Design/Operation) design Unknown
Boundary (Internal/External) unknown The articles do not mention any software failure incident related to the boundary of the failure incident being within or outside the system. Therefore, the information to determine whether the failure was within the system or outside the system is unknown.
Nature (Human/Non-human) human_actions (a) The software failure incident occurring due to non-human actions: - The articles do not mention any software failure incident specifically caused by non-human actions. The incidents discussed primarily revolve around brake parts failing in rail cars due to design flaws and material fatigue, rather than any software-related issues [10635]. (b) The software failure incident occurring due to human actions: - The failure of brake disc hubs in Metro's rail cars was primarily attributed to design flaws, material fatigue, and delayed maintenance due to funding issues and decision-making by Metro officials. The incidents were not directly linked to human actions introducing contributing factors that led to the software failure [10635].
Dimension (Hardware/Software) hardware (a) The software failure incident occurring due to hardware: - The article mentions issues with brake parts, specifically the brake disc hubs, on Metro's rail cars [10635]. - The hubs failed due to fatigue caused by operating conditions and design issues, leading to cracks in the hubs [10635]. - The article also discusses the replacement of the hubs with redesigned ones made of stronger material to address the hardware-related failures [10635]. (b) The software failure incident occurring due to software: - The articles do not mention any software-related failures or issues contributing to the incidents reported. Therefore, there is no information available regarding software-related failures in this context.
Objective (Malicious/Non-malicious) non-malicious (a) The articles do not mention any malicious intent or actions related to the software failure incident. [10635] (b) The software failure incident related to the brake parts in the rail cars was non-malicious. It was primarily due to design flaws, material issues, and operating conditions that led to the failure of the brake disc hubs. The failure was attributed to fatigue caused by vibrations and the design of the specific hub. The manufacturer, Knorr Brake, redesigned the hubs to address the issue, indicating a non-malicious intent to improve the system's reliability. [10635]
Intent (Poor/Accidental Decisions) unknown The articles do not mention any software failure incident related to poor decisions or accidental decisions. Therefore, the intent of the software failure incident in this case is unknown.
Capability (Incompetence/Accidental) unknown Unknown
Duration unknown The articles do not mention any software failure incident related to a permanent or temporary duration. Therefore, the duration of the software failure incident is unknown based on the provided articles.
Behaviour other (a) crash: The articles do not mention any specific software crash incidents related to the rail cars or their brake parts [10635]. (b) omission: There is no direct mention of the software omitting to perform its intended functions in the articles [10635]. (c) timing: The software failure incident related to the brake parts is not described as a timing issue where the system performed its intended functions too late or too early [10635]. (d) value: The software failure incident is related to the brake disc hubs on the rail cars, which are mechanical components, and not directly related to software performing its intended functions incorrectly [10635]. (e) byzantine: The articles do not describe the software failure incident as exhibiting byzantine behavior with inconsistent responses and interactions [10635]. (f) other: The software failure incident related to the brake disc hubs on the rail cars does not fall into the categories of crash, omission, timing, value, or byzantine behavior. The failure is more related to a mechanical issue with the brake parts rather than a software-related behavior [10635].

IoT System Layer

Layer Option Rationale
Perception None None
Communication None None
Application None None

Other Details

Category Option Rationale
Consequence no_consequence (a) death: People lost their lives due to the software failure - There is no mention of any deaths resulting from the software failure incident reported in the articles [10635].
Domain transportation (a) The failed system was related to the transportation industry, specifically the rail transportation system operated by Metro. The software failure incident involved brake parts in rail cars that were found to fail sooner than expected, leading to incidents where brake parts fell from trains, causing service disruptions and safety concerns [10635]. The rail cars affected were part of Metro's fleet, which is used for transporting passengers [10635].

Sources

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