Crews have successfully repaired a 1,000-foot section of damaged track, which Metro officials blamed on a “heat kink” caused when steel expands and warps.
On Sunday, with temperatures again in the triple digits, the system was operating with a 35 mph maximum speed limit on all above-ground tracks, and additional teams of inspectors were walking the rails looking for possible problems, Metro spokesman Dan Stessel said.
Shuttle buses ferried passengers between Fort Totten and Prince George’s Plaza on the Green Line on Sunday as crews worked on the tracks. But shuttle service ended Sunday night when one track was opened, Metro said.
Stessel said Sunday afternoon that the three derailed train cars had been removed from the track.
Heat kinks, also known as sun kinks, can affect rails during extreme weather.
Stessel said the system was on heightened alert in recent days because of the heat, and service was briefly interrupted Saturday on the Orange Line near Landover after a supervisor aboard a train spotted an apparent anomaly.
Stessel declined to say when the Green Line rail that buckled had last been inspected before the derailment.
“That is part of the investigation,” Stessel said. “I’m sure we’ll have that in a few days. It’s not that we don’t have an answer. We’re not releasing the answer.”
He also said Metro is taking steps to improve its track inspections.
Last week, the agency took delivery of a high-tech machine that monitors tracks for imperfections. The machine — a track geometry vehicle — uses ultrasound sensors, lasers and cameras to collect data that can help identify areas in need of repair. The machine should be in use by autumn after further testing and calibrating, he said.
“This has been something we’ve been looking to get for some time,” Stessel said.