How Parasitic Oscillations Contributed To WMATA's Worst-Ever Train Accident

By John Oncea, Editor

Parasitic oscillations are unwanted electronic oscillations that can occur in amplifying devices like audio amplifiers, RF amplifiers, and digital circuits. They can lead to erratic operation, damage equipment, and, in one instance, lead to tragedy.

Veronica “Ronnie” DuBose was born in Washington, D.C., and, after graduating high school in 1998, moved to Culpeper, VA, where she worked at Culpeper Health Care Center. In 2009, DuBose, now a 29-year-old mother of an 8-year-old son and 1-year-old daughter, returned to Northwest D.C. to attend nursing school. On June 22 of that year, she boarded Washington Metro Train 112, bound from Glenmont to Shady Grove, for her first day of classes.

At 5:02 p.m., Dubose and eight others were killed and 80 more injured when Train 112 rear-ended Train 214, which was stopped between the Takoma and Fort Totten stations while waiting for another train to leave the Fort Totten station. The accident remains the worst ever in the more than 30-year operating history of the regional transit service.

Fort Totten Station, June 22, 2009, 5:02 p.m.

The National Transportation Safety Board (NTSB) found that Train 214 had come to a stop entirely within the faulty circuit B2-304, making it effectively invisible to the automatic train control (ATC) system. Other trains had received speed commands of 0 when traveling through this circuit but had enough forward momentum to make it to the next circuit and resume detection and receipt of speed commands from the ATC system.

Train 214 was going slower than normal because it was being driven in manual mode by its operator, and it came to a stop while remaining on circuit B2-304 and was therefore invisible. Train 112 behind it was given full speed (55 mph) commands by the ATC to proceed on the track.

The investigation found that the emergency brakes had been applied by the operator of train 112 when train 214 came into view, but it was too late to avert the collision, which occurred at a speed of about 49 mph.

Further NTSB investigation found that, after a June 17 replacement of a track circuit component at what became the crash site, the track circuit had been suffering from parasitic oscillations that left it unable to reliably report when that stretch of track was occupied by a train.

What Are Parasitic Oscillations

Parasitic oscillations are unwanted, spontaneous oscillations that occur in electronic circuits, particularly those involving amplifiers and feedback systems, explains In Compliance. These oscillations are not part of the intended operation of the device and can arise when certain conditions – specifically, sufficient gain and the presence of unintended feedback – are met within a circuit.

At a particular frequency where the product of gain and feedback equals or exceeds one, and the phase shift is zero degrees, the circuit can begin to oscillate on its own, generating a signal that was not designed to be present.

The root cause of parasitic oscillations often lies in the physical layout of the circuit, such as the proximity of input and output traces, which can inadvertently couple signals back into earlier stages of the circuit. This unintended feedback loop can be exacerbated by parasitic elements such as capacitance, inductance, or resistance that exist inherently in all electronic components and wiring, especially in complex or densely packed systems, writes Toshiba. In power amplifiers, for example, parasitic capacitance and inductance can form resonant circuits that oscillate at specific frequencies.

Parasitic oscillations are problematic because they disrupt the normal function of electronic systems. In amplifiers, they can cause the output to become erratic, introduce noise, waste power, and generate excess heat, Cadence writes. In digital systems, they may lead to spurious signals, erratic counting, or malfunctioning logic stages. These oscillations also can result in electromagnetic interference (EMI), radiating unwanted signals that may affect other nearby electronic devices or systems.

To mitigate parasitic oscillations, engineers often employ techniques such as reducing circuit gain, introducing ferrite beads or resistors to dampen feedback paths, or redesigning the physical layout to minimize unintended coupling between circuit elements. Careful design and regular testing are essential to ensure that parasitic oscillations do not compromise system safety or reliability.

Parasitic Oscillations And The 2009 Fort Totten Collision

The NTSB determined that, in the context of the 2009 Fort Totten collision on the Washington Metro, parasitic oscillations played a critical role in the failure of the train detection system, which led to the fatal accident. The Metro’s ATC system relied on track circuits to detect the presence of trains and manage their movement safely. However, certain track circuit modules were susceptible to parasitic oscillations.

These oscillations could cause the track circuit to lose its ability to detect a train occupying a section of track, effectively rendering the train “invisible” to the ATC system. In the Fort Totten incident, the stopped train was entirely within a faulty track circuit that failed to register its presence due to such a malfunction. As a result, the ATC system erroneously allowed a following train to proceed at full speed, leading to a catastrophic rear-end collision.

The NTSB investigation found that the underlying cause was not just a hardware failure, but a systemic issue: Washington Metropolitan Area Transit Authority (WMATA) and its contractors had not adequately maintained or monitored the track circuits for spurious signals like parasitic oscillations, nor had they institutionalized enhanced testing procedures that could have detected the problem before the accident occurred.

WMATA Reacts To The NTSB Investigation

The tragic accident that led to DuBose’s death – along with those of train operator Jeanice McMillan and fellow passengers Ana Fernandez, Mary Doolittle, Dennis Hawkins, Lavonda King, Maj. Gen. David F. Wherley Jr. and his wife, Ann Wherley, and Cameron Williams, 36 – led the NTSB to call out Metro’s safety culture after the crash, saying “Metro was on a collision course long before this accident,” according to NBC Washington. The NTSB also said Metro had embraced a culture that did not put the safety of its passengers first.

It also resulted in several important changes in the intervening years, says WMATA General Manager and CEO Randy Clarke, including building up systems so knowledge remains after employees retire, digitizing records to allow data analysis, improving employee training, and becoming more transparent. “Trust is built on transparency, at the end of the day. I think that’s what we’re working on,” Clarke said.

Another response to the accident was the formation of the Washington Metrorail Safety Commission (WMSC) to track Metro safety. In addition, according to WMSC spokesperson Max Smith, the commission has enforcement authority. “The prior oversight agency could raise an issue. It could be fully supported but they didn't have that authority to make sure it really stuck and was addressed,” Smith explained.

Clarke feels it’s important to put the Metro’s safety record since the June 2009 accident in perspective, saying, “We are either leading or above average on every safety metric in the country for a rail system – so, the safest rail system in the country. Does that mean we’re perfect? No. There’s going to be things that happen … Even if we have some type of issue with Metro, we are not having crises or catastrophic incidents.”

WMATA’s Plan To Prevent Parasitic Oscillations

After the 2009 Fort Totten collision, WMATA suspended Automatic Train Operation (ATO) due to a safety hazard known as parasitic oscillation, GGWash writes. In addition, WMATA identified that Alstom Generation II Audio Frequency Track Circuit (AFTC) modules were susceptible to parasitic oscillations, which could cause a loss of train detection.

Beginning in 2012, WMATA systematically replaced all Alstom Generation II AFTC modules with Ansaldo AF-800W AFTC modules, which eliminated the parasitic oscillation hazard. The replacement was prioritized on the Red Line, with all Generation II modules removed before ATO was reactivated on that segment.

Before full replacement, WMATA installed ferrite chokes on affected circuits to suppress parasitic oscillations, reducing their effect to a non-risk status. They also upgraded negative return cables and started a rail grinding program to further stabilize track circuit performance and minimize non-critical failures.

WMATA instituted semi-annual inspection and testing of track circuits to detect and address any recurrence of parasitic oscillations, as well as invested in advanced diagnostic tools, such as infrared imaging and spectrum analyzers, to improve the ability to monitor and maintain the system.

Finally, WMATA conducted a system-wide safety analysis, as recommended by the NTSB, to evaluate all foreseeable failures, including parasitic oscillation and other potential hazards. The process included organizational changes, updated procedures, and coordination with oversight bodies to ensure all safety measures were in place before reintroducing ATO.

WMATA’s approach to preventing parasitic oscillations when returning to ATO involved a combination of hardware replacement, interim mitigation, enhanced testing, and comprehensive safety analysis. The core solution was the complete replacement of susceptible track circuit modules, supported by rigorous certification and oversight processes.

15 Years Later

WMATA announced last December that, for the first time in 15 years, Metro trains would return to ATO, a move that allows the system to operate as it was originally designed and assist train operators with their duties.

ATO controls the trains’ acceleration, deceleration, and speed while being regulated by safety-critical equipment. Trains will get signal and speed commands from equipment located between the tracks for a smoother ride, enhanced safety, and improved on-time performance. Metro will operate in semi-automated mode with a train operator always inside the operator’s cab.

According to WMATA, “ATO will improve the experience for customers and train operators alike, allowing for coordinated arrivals at transfer stations and improved efficiency for customers transferring lines. Operators will remain responsible for the safety of the customers aboard their trains. ATO will not be used during inclement weather, during single tracking, when workers are on the roadway, and in other conditions.”

WMATA included several additional layers of protection to improve safety for customers and train operators when trains run in ATO mode, including:

• Implementation of preventative maintenance cycles that align with manufacturer recommendations
• Adjustment of track marker coils to track train location more precisely
• Implementation of train detection tools, which pair with our control center software solution, to allow traffic controllers to act on potential safety risks
• Replacement of older generation track circuits with a new, more dependable model

Metro has been preparing those whose roles include operating, controlling, and maintaining ATO for several months. The training was designed by Metro in coordination with Metro’s Safety & Readiness department and reviewed by the WMSC. Training includes classroom and simulator exercises, including the use of procedures that match real-life operations.

Where Things Stand Today

WMATA resumed ATO on the Red Line on December 15, 2024, marking the first use of automated train control in the system since it was suspended following the 2009 Red Line crash. The relaunch was described by WMATA leadership as a historic milestone, promising smoother rides, increased efficiency, and improved on-time performance.

In preparation, WMATA upgraded track circuits, improved train detection, and adjusted track marker coils for better train location precision. Operators and control staff underwent extensive retraining and simulation exercises; however, significant issues have emerged:

• Station Overruns: Since ATO’s return, trains have overrun station platforms on the Red Line more than 220 times (as of early April 2025), a dramatic increase over the 144 overruns recorded across the entire Metrorail system in 2023, according to Trains.com. About 38% of these incidents involve three or more cars overshooting the platform.
• Safety Commission Concerns: The WMSC considers these overruns a safety issue, citing risks to passengers and workers, such as passengers being unable to safely disembark or evacuate during emergencies. As a result, it has blocked WMATA from expanding ATO to other lines until the overruns are significantly reduced and the root cause is addressed.
• WMATA’s Position: WMATA disputes the severity of the overruns, arguing that the Federal Transit Administration (FTA) and peer agencies treat such events as reliability, not safety, problems. WMATA reports a 99.97% reliability rate for platform stops over the past three months, and notes that no ATO-operated train has run a red signal since the relaunch, while human operators have had three such incidents.
• Industry Benchmarking: WMATA’s peer agencies do not track overruns as safety events, and their reliability rates are comparable (around 99.98%), notes WMATA.

The WMSC has made it clear that ATO cannot be expanded to other lines until the Red Line’s overruns are reduced and explained. The commission has even suggested involving federal investigators (NTSB) to help diagnose the technical issues, NBC Washington reports.

WMATA has formed cross-functional working groups, updated procedures, and conducted targeted testing (e.g., at Judiciary Square) to address overruns, and the Metro Board of Directors is actively discussing the future of ATO and the platform overrun issue in their meetings. Despite the commission’s stance, WMATA maintains it is technically ready to implement ATO on the Green Line and other lines by summer 2025, pending regulatory approval.

WMATA’s return to ATO on the Red Line has delivered technical and operational improvements, but frequent station overruns have led the safety commission to halt expansion to other lines until the issues are resolved. The timeline for broader ATO rollout now depends on WMATA’s ability to address these concerns and secure regulatory approval.