Riders balance on a ledge, leaning out to look for an oncoming train, while walking back to the University of Washington Station… (Photo courtesy Daniel Heppner) 

The weight of a fully loaded light-rail train triggered the post-Apple Cup stall Nov. 26, when inadequate communications led stranded passengers to walk out along the underground tracks, Sound Transit said Wednesday.

Sound Transit CEO Peter Rogoff called the stall a “preventable mechanical failure.”

When the new Siemens train filled with riders, its coil suspension sagged, providing less clearance over trackway devices than usual, the inquiry found.

Read Mike Lindblom’s reporting in the Seattle Times