Sound Transit Suspends 1 and 2 Lines After 4-Car Train Derails in Seattle

Q: What specific mechanical failure caused track bolts to shear and trigger only the second derailment in Sound Transit's history?

It has not been publicly identified. Based on the reporting provided, Sound Transit said crews found sheared track bolts and was still investigating, but neither the agency nor the cited coverage named a specific mechanical failure that caused those bolts to shear. What is known is that the lead car derailed at low speed while moving through a crossover near International District/Chinatown Station, and the damaged train then blocked both tracks in the downtown tunnel. Cleanup required removing the sheared bolts and shutting off overhead power, which points investigators toward the switch or crossover infrastructure, fasteners, and related track components. So the most accurate answer is that the precise failure mechanism remained undetermined in public reporting at the time. Any firmer claim — such as a failed switch component, broken fastener assembly, or vehicle-wheel interaction problem — would be speculation until Sound Transit or investigators release findings.

1 articles · Updated · The Seattle Times · Aug 2

Service was still halted across downtown Seattle at 10 a.m. Sunday after a four-car Sound Transit train derailed around midnight at International District/Chinatown Station with no passengers aboard.
The lead railcar left the track at low speed while crossing from the northbound track toward the southbound platform to pick up Ed Sheeran concert riders, shearing bolts and blocking both directions.
Shuttle buses replaced rail service between Capitol Hill, Sodo, downtown stations and Judkins Park, while 1 Line and 2 Line trains continued operating on shortened segments with platform changes and some turnbacks.
The disruption again exposed the lack of a downtown crossover track, which transit experts have recommended to avoid shutting all four downtown stations when one or both tracks are blocked.
Sound Transit said this was only its second known passenger-service derailment; the other, in 2009 near the Sodo yard, caused a 50-minute delay.