Stray current, a backlog of power system repairs and a lack of backup electrical sources are mostly to blame for light rail stalls that have inconvenienced thousands of riders, a new consultant’s report for Sound Transit says.
Power supply interruptions caused 239 hours of train delays or shutdowns in spots along the 1 Line between Lynnwood, Seattle and SeaTac in the first 11 months of last year, according to a Sound Transit internal review, also released Thursday. About 95 hours of disruptions were triggered by signal malfunctions.
The report found a fundamental and pervasive shortcoming: Train power and control systems throughout Sound Transit’s network are “more complex than necessary.”
For instance, the network is also unusually susceptible to minor fluctuations in power, which can trigger outages, according to the report.
In all, there were 177 incidents — some lasting minutes, some several hours — of passenger trips interrupted by power, mechanical or signal and dispatch breakdowns in the 11 months. Those added up to 432 hours of reduced service, or about 10 standard workweeks.
The Thursday reports, from the consultant and the internal review, provide the most detailed accounting to date of the technical problems light rail faces, and possible actions to fix them.
The consequences of Sound Transit’s breakdowns are real for up to 100,000 daily passengers, ridership that has been growing since the new Northgate-Lynnwood extension opened last summer. Travelers are finding the system less reliable and are forced to suddenly change plans after seeing vague rider alerts about closures, or arriving at stations to find crowds waiting for trains 30 minutes apart instead of every 10 minutes.
Sound Transit CEO Goran Sparrman commissioned the $500,000 report by engineering firm HNTB’s Bellevue division, after a wave of breakdowns in mid-2024, including a damaged overhead power line at UW Station that blocked the northbound track most of Sept. 17.
Political and agency leaders in Seattle are obsessed with solving problems before six FIFA World Cup soccer matches begin here in June 2026, to avoid the shame of international travelers encountering botched transit or highways. There is also growing acknowledgment that customers are questioning the dependability of light rail.
“My north star is not the World Cup,” said Russ Arnold, deputy CEO for service delivery. “Our passengers deserve (reliability), the ones that use it every single day, not just the people that are going to come for a big event.”
The 68-page report contains 79 recommendations stretching beyond power systems, to deal with weak governance, inefficient use of maintenance crews and a lack of crossover rail switches to skip blockages.
Sound Transit is still examining the report and will issue a formal response in about three months, said Moises Gutierrez, deputy CEO for agency oversight. To make every suggested change would require tens, maybe hundreds of millions of dollars and several years.
Sound Transit is pursuing inexpensive “quick wins” at a cost of $1.3 million this winter, Gutierrez said. Examples are high-tech devices to measure wear and tear on overhead power equipment, cleaning tunnel drains where debris caused stray current and train operator education to troubleshoot minor stalls.
Since improvement efforts started in November, hours of disrupted service were lowered by half, to 2.5 hours per month, but more gains are needed, Gutierrez reported Thursday to a transit board committee. Trains are stalling more often but workers are restarting them quicker, he said.
Power losses
Sound Transit’s highly sensitive network for controlling electric current, known as “Rail to Ground,” has triggered train stalls, including 14 hours of false alarms. Tracks aren’t grounded, so electricity must loop from the overhead catenary wires to the train motors down to the rails, then back up to the substation. Stray current is bad because it corrodes the rails and at extreme levels can shock people.
Sound Transit’s detection system was designed to provide an extra safety margin.
The problem is substations trip off whenever the proper current doesn’t return, commonly in the tunnel under the University of Washington. It remains unclear why voltages are spiking, the review team said. HNTB said rail systems in Boston, Chicago and Philadelphia operate safely without Rail to Ground.
Sound Transit’s Arnold replied that light rail would need high-tech monitoring devices, or more human technicians, to change its current methods. More research is needed to know if that’s a good trade-off, he said.
HNTB found an imbalance where train power crews spent 53% of their time doing preventive maintenance and only 11% on repairs, so a typical repair is delayed three to six months, sometimes two years. Sound Transit agreed the “trade is not being staffed and managed in a way compatible with maintaining a state of good repair.”
Nearly 70% of power repairs required more than one crew trip because of poor coordination, complexity and a lack of time, mainly four hours overnight. Gutierrez said King County Metro, which operates light rail for Sound Transit, is already reorganizing power supply crews and “they’ve done great.”
Trains themselves malfunctioned, causing stalls similar to a power outage, because of contaminants in hydraulic brake fluid and pressure leaks. Railcar maker Siemens and the brake vendor are running test trains to find solutions, Sound Transit reported.
The consultant report minces few words about the UW Station incident: Metro and Sound Transit could not prove their theory that the overhead wire was too slack before a damaged pantograph on a train roof got tangled in the wire. Transit staff chose to move a stalled train without fully understanding the damage, making it worse. A lack of spare parts delayed repairs. UW Station wires were finally replaced in early February.
Inspections also noted areas of risk.
While examining tips from workers, “inspections revealed evidence of aging infrastructure, poorly arranged gear that limited adequate access for maintenance, and overheated equipment caused by inadequate HVAC (heating, ventilation, air conditioning) systems.” The independent team discovered neglected components at UW Station and high temperatures near control-center computers in Sodo.
In multiple spots, a lone public utility line powers one or even two train substations, where storms have halted the trains. This situation is one of many “single points of failure” that continue putting service at risk, the HNTB report said. Sound Transit long ago designed a 1,500-volt network
Some solutions are dedicated lines that go exclusively into transit substations and mobile generators to pinch-hit if a substation fails. Boston’s new Green Line extension requires a “minimum of two independent supplies” to provide redundancy, the report emphasized.
Some historical decisions help explain why Sound Transit — whose high project costs have been blamed on “overcustomization” to satisfy political and community requests — is saddled with complex systems and obsolete parts: The downtown train tunnel was built by Metro for buses in the late 1980s and adapted to trains later. Also, designers minimized the number of substations systemwide to save money, reduce land takings and improve aesthetics.
Breakdowns suddenly increased in mid-2024 because new station and track openings added electrical and other stress to the system, Gutierrez said.
CEO Goran Sparrman emphasized how these pains show that Sound Transit, after two decades of building light rail lines, is changing from just a delivery agency to operating a complex system.
Crossover switches
HNTB recommends adding crossover tracks just south of Lynnwood City Center Station and Symphony or Pioneer Square stations in downtown. This would let trains go around minor problem spots, help Sound Transit maintain the frequency of every four minutes that’s promised in 2026 and allow more daytime maintenance without paralyzing the 33-mile network.
Arnold said a downtown crossover seems more feasible than rebuilding elevated tracks at Lynnwood.
The independent report also challenged how the relationship between Sound Transit and Metro is governed.
The longstanding operations agreement between Sound Transit and Metro, which handles maintenance and operations, is too loose and should be replaced by an enforceable contract with financial penalties, the report says. “Sound Transit cannot directly enforce performance standards or hold Metro fully accountable for operational deficiencies.” From Metro workers’ perspective, relations are “siloed” so it’s hard to know what should get fixed first.
The report mentioned Chicago, Philadelphia, New York and Los Angeles, where operating agencies were absorbed or merged with regional transit owners.
Metro responded it’s been a successful partner since 2009 and added staff when Sound Transit opened 12 rail stations last year, amid a nationwide shortage of transit operators. “Metro upholds the highest standards of service, with a focus on accessibility, cleanliness, reliability, safety and customer satisfaction” and will collaborate on technical improvements, spokesperson Sean Hawks wrote.
Arnold said the agreement will be tightened this year to define performance but without financial penalties or incentives. If Metro were fined, those funds would likely come from other transit, namely local buses, van service or water taxis, Arnold noted, but consultants didn’t cross that hurdle in the big report.
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